diff --git a/OpenRA.Editor/BrushTool.cs b/OpenRA.Editor/BrushTool.cs
index 220fdacb56..e41fe45171 100644
--- a/OpenRA.Editor/BrushTool.cs
+++ b/OpenRA.Editor/BrushTool.cs
@@ -37,16 +37,15 @@ namespace OpenRA.Editor
 			for (var u = 0; u < template.Size.X; u++)
 				for (var v = 0; v < template.Size.Y; v++)
 				{
-					if (surface.Map.IsInMap(new CVec(u, v) + pos))
+					var cell = pos + new CVec(u, v);
+					if (surface.Map.Contains(cell))
 					{
 						var z = u + v * template.Size.X;
 						if (tile[z].Length > 0)
-							surface.Map.MapTiles.Value[u + pos.X, v + pos.Y] =
-								new TileReference<ushort, byte>
-								{
-									Type = brushTemplate.N,
-									Index = template.PickAny ? (byte)((u + pos.X) % 4 + ((v + pos.Y) % 4) * 4) : (byte)z,
-								};
+						{
+							var index = template.PickAny ? (byte)((u + pos.X) % 4 + ((v + pos.Y) % 4) * 4) : (byte)z;
+							surface.Map.MapTiles.Value[cell] = new TerrainTile(brushTemplate.N, index);
+						}
 
 						var ch = new int2((pos.X + u) / Surface.ChunkSize, (pos.Y + v) / Surface.ChunkSize);
 						if (surface.Chunks.ContainsKey(ch))
@@ -70,14 +69,15 @@ namespace OpenRA.Editor
 		void FloodFillWithBrush(Surface s, CPos pos)
 		{
 			var queue = new Queue<CPos>();
-			var replace = s.Map.MapTiles.Value[pos.X, pos.Y];
+			var replace = s.Map.MapTiles.Value[pos];
 			var touched = new bool[s.Map.MapSize.X, s.Map.MapSize.Y];
 
 			Action<int, int> maybeEnqueue = (x, y) =>
 			{
-				if (s.Map.IsInMap(x, y) && !touched[x, y])
+				var c = new CPos(x, y);
+				if (s.Map.Contains(c) && !touched[x, y])
 				{
-					queue.Enqueue(new CPos(x, y));
+					queue.Enqueue(c);
 					touched[x, y] = true;
 				}
 			};
@@ -86,7 +86,7 @@ namespace OpenRA.Editor
 			while (queue.Count > 0)
 			{
 				var p = queue.Dequeue();
-				if (s.Map.MapTiles.Value[p.X, p.Y].Type != replace.Type)
+				if (s.Map.MapTiles.Value[p].Type != replace.Type)
 					continue;
 
 				var a = FindEdge(s, p, new CVec(-1, 0), replace);
@@ -94,10 +94,10 @@ namespace OpenRA.Editor
 
 				for (var x = a.X; x <= b.X; x++)
 				{
-					s.Map.MapTiles.Value[x, p.Y] = new TileReference<ushort, byte> { Type = brushTemplate.N, Index = (byte)0 };
-					if (s.Map.MapTiles.Value[x, p.Y - 1].Type == replace.Type)
+					s.Map.MapTiles.Value[new CPos(x, p.Y)] = new TerrainTile(brushTemplate.N, (byte)0);
+					if (s.Map.MapTiles.Value[new CPos(x, p.Y - 1)].Type == replace.Type)
 						maybeEnqueue(x, p.Y - 1);
-					if (s.Map.MapTiles.Value[x, p.Y + 1].Type == replace.Type)
+					if (s.Map.MapTiles.Value[new CPos(x, p.Y + 1)].Type == replace.Type)
 						maybeEnqueue(x, p.Y + 1);
 				}
 			}
@@ -107,13 +107,13 @@ namespace OpenRA.Editor
 			s.Chunks.Clear();
 		}
 
-		static CPos FindEdge(Surface s, CPos p, CVec d, TileReference<ushort, byte> replace)
+		static CPos FindEdge(Surface s, CPos p, CVec d, TerrainTile replace)
 		{
 			for (;;)
 			{
 				var q = p + d;
-				if (!s.Map.IsInMap(q)) return p;
-				if (s.Map.MapTiles.Value[q.X, q.Y].Type != replace.Type) return p;
+				if (!s.Map.Contains(q)) return p;
+				if (s.Map.MapTiles.Value[q].Type != replace.Type) return p;
 				p = q;
 			}
 		}
diff --git a/OpenRA.Editor/Form1.cs b/OpenRA.Editor/Form1.cs
index 51d7c68441..c108f0b690 100644
--- a/OpenRA.Editor/Form1.cs
+++ b/OpenRA.Editor/Form1.cs
@@ -641,7 +641,8 @@ namespace OpenRA.Editor
 			for (var i = 0; i < surface1.Map.MapSize.X; i++)
 				for (var j = 0; j < surface1.Map.MapSize.Y; j++)
 				{
-					if (surface1.Map.MapResources.Value[i, j].Type != 0)
+					var cell = new CPos(i, j);
+					if (surface1.Map.MapResources.Value[cell].Type != 0)
 						totalResource += GetResourceValue(i, j);
 				}
 
@@ -654,9 +655,12 @@ namespace OpenRA.Editor
 			for (var u = -1; u < 2; u++)
 				for (var v = -1; v < 2; v++)
 				{
-					if (!surface1.Map.IsInMap(new CPos(x + u, y + v)))
+					var cell = new CPos(x + u, y + v);
+
+					if (!surface1.Map.Contains(cell))
 						continue;
-					if (surface1.Map.MapResources.Value[x + u, y + v].Type == resourceType)
+
+					if (surface1.Map.MapResources.Value[cell].Type == resourceType)
 						++sum;
 				}
 
@@ -666,7 +670,7 @@ namespace OpenRA.Editor
 		int GetResourceValue(int x, int y)
 		{
 			var imageLength = 0;
-			int type = surface1.Map.MapResources.Value[x, y].Type;
+			var type = surface1.Map.MapResources.Value[new CPos(x, y)].Type;
 			var template = surface1.ResourceTemplates.FirstOrDefault(a => a.Value.Info.ResourceType == type).Value;
 			if (type == 1)
 				imageLength = 12;
diff --git a/OpenRA.Editor/ResourceTool.cs b/OpenRA.Editor/ResourceTool.cs
index f8f6351e05..b135daaf0d 100644
--- a/OpenRA.Editor/ResourceTool.cs
+++ b/OpenRA.Editor/ResourceTool.cs
@@ -21,12 +21,9 @@ namespace OpenRA.Editor
 
 		public void Apply(Surface surface)
 		{
-			surface.Map.MapResources.Value[surface.GetBrushLocation().X, surface.GetBrushLocation().Y]
-				= new TileReference<byte, byte>
-				{
-					Type = (byte)resourceTemplate.Info.ResourceType,
-					Index = (byte)random.Next(resourceTemplate.Info.MaxDensity)
-				};
+			var type = (byte)resourceTemplate.Info.ResourceType;
+			var index = (byte)random.Next(resourceTemplate.Info.MaxDensity);
+			surface.Map.MapResources.Value[surface.GetBrushLocation()] = new ResourceTile(type, index);
 
 			var ch = new int2(surface.GetBrushLocation().X / Surface.ChunkSize,
 				surface.GetBrushLocation().Y / Surface.ChunkSize);
diff --git a/OpenRA.Editor/Surface.cs b/OpenRA.Editor/Surface.cs
index 4d4fb25892..16fcb1f678 100644
--- a/OpenRA.Editor/Surface.cs
+++ b/OpenRA.Editor/Surface.cs
@@ -62,8 +62,8 @@ namespace OpenRA.Editor
 		public bool ShowRuler;
 
 		public bool IsPaste { get { return TileSelection != null && ResourceSelection != null; } }
-		public TileReference<ushort, byte>[,] TileSelection;
-		public TileReference<byte, byte>[,] ResourceSelection;
+		public TerrainTile[,] TileSelection;
+		public ResourceTile[,] ResourceSelection;
 		public CPos SelectionStart;
 		public CPos SelectionEnd;
 
@@ -206,9 +206,9 @@ namespace OpenRA.Editor
 			var key = Map.Actors.Value.FirstOrDefault(a => a.Value.Location() == brushLocation);
 			if (key.Key != null) Map.Actors.Value.Remove(key.Key);
 
-			if (Map.MapResources.Value[brushLocation.X, brushLocation.Y].Type != 0)
+			if (Map.MapResources.Value[brushLocation].Type != 0)
 			{
-				Map.MapResources.Value[brushLocation.X, brushLocation.Y] = new TileReference<byte, byte>();
+				Map.MapResources.Value[brushLocation] = new ResourceTile(0, 0);
 				var ch = new int2(brushLocation.X / ChunkSize, brushLocation.Y / ChunkSize);
 				if (Chunks.ContainsKey(ch))
 				{
@@ -271,7 +271,8 @@ namespace OpenRA.Editor
 				for (var i = 0; i < ChunkSize; i++)
 					for (var j = 0; j < ChunkSize; j++)
 					{
-						var tr = Map.MapTiles.Value[u * ChunkSize + i, v * ChunkSize + j];
+						var cell = new CPos(u * ChunkSize + i, v * ChunkSize + j);
+						var tr = Map.MapTiles.Value[cell];
 						var tile = TileSetRenderer.Data(tr.Type);
 						var index = (tr.Index < tile.Count) ? tr.Index : (byte)0;
 						var rawImage = tile[index];
@@ -279,9 +280,9 @@ namespace OpenRA.Editor
 							for (var y = 0; y < TileSetRenderer.TileSize; y++)
 								p[(j * TileSetRenderer.TileSize + y) * stride + i * TileSetRenderer.TileSize + x] = Palette.GetColor(rawImage[x + TileSetRenderer.TileSize * y]).ToArgb();
 
-						if (Map.MapResources.Value[u * ChunkSize + i, v * ChunkSize + j].Type != 0)
+						if (Map.MapResources.Value[cell].Type != 0)
 						{
-							var resourceImage = ResourceTemplates[Map.MapResources.Value[u * ChunkSize + i, v * ChunkSize + j].Type].Bitmap;
+							var resourceImage = ResourceTemplates[Map.MapResources.Value[cell].Type].Bitmap;
 							var srcdata = resourceImage.LockBits(resourceImage.Bounds(),
 								ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
 
@@ -508,16 +509,17 @@ namespace OpenRA.Editor
 			var width = Math.Abs((start - end).X);
 			var height = Math.Abs((start - end).Y);
 
-			TileSelection = new TileReference<ushort, byte>[width, height];
-			ResourceSelection = new TileReference<byte, byte>[width, height];
+			TileSelection = new TerrainTile[width, height];
+			ResourceSelection = new ResourceTile[width, height];
 
 			for (var x = 0; x < width; x++)
 			{
 				for (var y = 0; y < height; y++)
 				{
 					// TODO: crash prevention
-					TileSelection[x, y] = Map.MapTiles.Value[start.X + x, start.Y + y];
-					ResourceSelection[x, y] = Map.MapResources.Value[start.X + x, start.Y + y];
+					var cell = new CPos(start.X + x, start.Y + y);
+					TileSelection[x, y] = Map.MapTiles.Value[cell];
+					ResourceSelection[x, y] = Map.MapResources.Value[cell];
 				}
 			}
 		}
@@ -534,10 +536,11 @@ namespace OpenRA.Editor
 				{
 					var mapX = loc.X + x;
 					var mapY = loc.Y + y;
+					var cell = new CPos(mapX, mapY);
 
 					// TODO: crash prevention for outside of bounds
-					Map.MapTiles.Value[mapX, mapY] = TileSelection[x, y];
-					Map.MapResources.Value[mapX, mapY] = ResourceSelection[x, y];
+					Map.MapTiles.Value[cell] = TileSelection[x, y];
+					Map.MapResources.Value[cell] = ResourceSelection[x, y];
 
 					var ch = new int2(mapX / ChunkSize, mapY / ChunkSize);
 					if (Chunks.ContainsKey(ch))
diff --git a/OpenRA.Game/GameRules/WeaponInfo.cs b/OpenRA.Game/GameRules/WeaponInfo.cs
index b554a2271e..ef7bb5bbfc 100644
--- a/OpenRA.Game/GameRules/WeaponInfo.cs
+++ b/OpenRA.Game/GameRules/WeaponInfo.cs
@@ -180,7 +180,7 @@ namespace OpenRA.GameRules
 			if (target.Type == TargetType.Terrain)
 			{
 				var cell = target.CenterPosition.ToCPos();
-				if (!world.Map.IsInMap(cell))
+				if (!world.Map.Contains(cell))
 					return false;
 
 				var cellInfo = world.Map.GetTerrainInfo(cell);
diff --git a/OpenRA.Game/Graphics/Minimap.cs b/OpenRA.Game/Graphics/Minimap.cs
index d99d02cdbc..c766273883 100644
--- a/OpenRA.Game/Graphics/Minimap.cs
+++ b/OpenRA.Game/Graphics/Minimap.cs
@@ -74,8 +74,9 @@ namespace OpenRA.Graphics
 							continue;
 
 						var res = resourceRules.Actors["world"].Traits.WithInterface<ResourceTypeInfo>()
-								.Where(t => t.ResourceType == map.MapResources.Value[mapX, mapY].Type)
+							.Where(t => t.ResourceType == map.MapResources.Value[mapX, mapY].Type)
 								.Select(t => t.TerrainType).FirstOrDefault();
+
 						if (res == null)
 							continue;
 
@@ -135,7 +136,7 @@ namespace OpenRA.Graphics
 
 					var color = t.Trait.RadarSignatureColor(t.Actor);
 					foreach (var cell in t.Trait.RadarSignatureCells(t.Actor))
-						if (world.Map.IsInMap(cell))
+						if (world.Map.Contains(cell))
 							*(c + ((cell.Y - world.Map.Bounds.Top) * bitmapData.Stride >> 2) + cell.X - world.Map.Bounds.Left) = color.ToArgb();
 				}
 			}
diff --git a/OpenRA.Game/Graphics/TerrainRenderer.cs b/OpenRA.Game/Graphics/TerrainRenderer.cs
index fe6cb84410..7d55487720 100644
--- a/OpenRA.Game/Graphics/TerrainRenderer.cs
+++ b/OpenRA.Game/Graphics/TerrainRenderer.cs
@@ -28,15 +28,12 @@ namespace OpenRA.Graphics
 			var vertices = new Vertex[4 * map.Bounds.Height * map.Bounds.Width];
 			var nv = 0;
 
-			for (var j = map.Bounds.Top; j < map.Bounds.Bottom; j++)
+			foreach (var cell in map.Cells)
 			{
-				for (var i = map.Bounds.Left; i < map.Bounds.Right; i++)
-				{
-					var tile = wr.Theater.TileSprite(map.MapTiles.Value[i, j]);
-					var pos = wr.ScreenPosition(new CPos(i, j).CenterPosition) - 0.5f * tile.size;
-					Util.FastCreateQuad(vertices, pos, tile, terrainPalette, nv, tile.size);
-					nv += 4;
-				}
+				var tile = wr.Theater.TileSprite(map.MapTiles.Value[cell]);
+				var pos = wr.ScreenPosition(cell.CenterPosition) - 0.5f * tile.size;
+				Util.FastCreateQuad(vertices, pos, tile, terrainPalette, nv, tile.size);
+				nv += 4;
 			}
 
 			vertexBuffer = Game.Renderer.Device.CreateVertexBuffer(vertices.Length);
@@ -46,9 +43,9 @@ namespace OpenRA.Graphics
 		public void Draw(WorldRenderer wr, Viewport viewport)
 		{
 			var verticesPerRow = 4*map.Bounds.Width;
-			var bounds = viewport.CellBounds;
-			var firstRow = bounds.Top - map.Bounds.Top;
-			var lastRow = bounds.Bottom - map.Bounds.Top;
+			var cells = viewport.VisibleCells;
+			var firstRow = cells.TopLeft.Y - map.Bounds.Top;
+			var lastRow = cells.BottomRight.Y - map.Bounds.Top + 1;
 
 			if (lastRow < 0 || firstRow > map.Bounds.Height)
 				return;
diff --git a/OpenRA.Game/Graphics/Theater.cs b/OpenRA.Game/Graphics/Theater.cs
index c7b136b5ed..141e3ddd02 100644
--- a/OpenRA.Game/Graphics/Theater.cs
+++ b/OpenRA.Game/Graphics/Theater.cs
@@ -71,7 +71,7 @@ namespace OpenRA.Graphics
 			missingTile = sheetBuilder.Add(new byte[1], new Size(1, 1));
 		}
 
-		public Sprite TileSprite(TileReference<ushort, byte> r)
+		public Sprite TileSprite(TerrainTile r)
 		{
 			Sprite[] template;
 			if (!templates.TryGetValue(r.Type, out template))
diff --git a/OpenRA.Game/Graphics/Viewport.cs b/OpenRA.Game/Graphics/Viewport.cs
index 4c61e2e18c..1dd6a5f881 100755
--- a/OpenRA.Game/Graphics/Viewport.cs
+++ b/OpenRA.Game/Graphics/Viewport.cs
@@ -9,6 +9,7 @@
 #endregion
 
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Drawing;
 using System.Linq;
@@ -46,7 +47,8 @@ namespace OpenRA.Graphics
 		public int2 TopLeft { get { return CenterLocation - viewportSize / 2; } }
 		public int2 BottomRight { get { return CenterLocation + viewportSize / 2; } }
 		int2 viewportSize;
-		bool cellBoundsDirty = true;
+		CellRegion cells;
+		bool cellsDirty = true;
 
 		float zoom = 1f;
 		public float Zoom
@@ -60,7 +62,7 @@ namespace OpenRA.Graphics
 			{
 				zoom = value;
 				viewportSize = (1f / zoom * new float2(Game.Renderer.Resolution)).ToInt2();
-				cellBoundsDirty = true;
+				cellsDirty = true;
 			}
 		}
 
@@ -110,14 +112,14 @@ namespace OpenRA.Graphics
 		public void Center(WPos pos)
 		{
 			CenterLocation = worldRenderer.ScreenPxPosition(pos).Clamp(mapBounds);
-			cellBoundsDirty = true;
+			cellsDirty = true;
 		}
 
 		public void Scroll(float2 delta, bool ignoreBorders)
 		{
 			// Convert scroll delta from world-px to viewport-px
 			CenterLocation += (1f / Zoom * delta).ToInt2();
-			cellBoundsDirty = true;
+			cellsDirty = true;
 
 			if (!ignoreBorders)
 				CenterLocation = CenterLocation.Clamp(mapBounds);
@@ -129,33 +131,30 @@ namespace OpenRA.Graphics
 		{
 			get
 			{
-				var r = CellBounds;
-				var ctl = new CPos(r.Left, r.Top).TopLeft;
-				var cbr = new CPos(r.Right, r.Bottom).TopLeft;
+				var ctl = VisibleCells.TopLeft.TopLeft;
+				var cbr = VisibleCells.BottomRight.BottomRight;
 				var tl = WorldToViewPx(worldRenderer.ScreenPxPosition(ctl)).Clamp(ScreenClip);
 				var br = WorldToViewPx(worldRenderer.ScreenPxPosition(cbr)).Clamp(ScreenClip);
 				return Rectangle.FromLTRB(tl.X, tl.Y, br.X, br.Y);
 			}
 		}
 
-		// Rectangle (in cell coords) of cells that are currently visible on the screen
-		Rectangle cachedRect;
-		public Rectangle CellBounds
+		public CellRegion VisibleCells
 		{
 			get
 			{
-				if (cellBoundsDirty)
+				if (cellsDirty)
 				{
-					var boundary = new CVec(1, 1);
-					var tl = worldRenderer.Position(TopLeft).ToCPos() - boundary;
-					var br = worldRenderer.Position(BottomRight).ToCPos() + boundary;
+					// Calculate the intersection of the visible rectangle and the map.
+					var map = worldRenderer.world.Map;
+					var tl = map.Clamp(worldRenderer.Position(TopLeft).ToCPos() - new CVec(1, 1));
+					var br = map.Clamp(worldRenderer.Position(BottomRight).ToCPos());
 
-					cachedRect = Rectangle.Intersect(Rectangle.FromLTRB(tl.X, tl.Y, br.X, br.Y), worldRenderer.world.Map.Bounds);
-					cellBoundsDirty = false;
+					cells = new CellRegion(tl, br);
+					cellsDirty = false;
 				}
 
-				var b = worldRenderer.world.VisibleBounds;
-				return b.HasValue ? Rectangle.Intersect(cachedRect, b.Value) : cachedRect;
+				return cells;
 			}
 		}
 	}
diff --git a/OpenRA.Game/Map/CellLayer.cs b/OpenRA.Game/Map/CellLayer.cs
new file mode 100644
index 0000000000..7f973b8902
--- /dev/null
+++ b/OpenRA.Game/Map/CellLayer.cs
@@ -0,0 +1,105 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation. For more information,
+ * see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Drawing;
+using OpenRA.Graphics;
+
+namespace OpenRA
+{
+	// Represents a layer of "something" that covers the map
+	public class CellLayer<T> : IEnumerable<T>
+	{
+		public readonly Size Size;
+		T[] entries;
+
+		public CellLayer(Map map)
+			: this(new Size(map.MapSize.X, map.MapSize.Y)) { }
+
+		public CellLayer(Size size)
+		{
+			Size = size;
+			entries = new T[size.Width * size.Height];
+		}
+
+		// Resolve an array index from cell coordinates
+		int Index(CPos cell)
+		{
+			// This will eventually define a distinct case for diagonal cell grids
+			return cell.Y * Size.Width + cell.X;
+		}
+
+		/// <summary>Gets or sets the <see cref="OpenRA.CellLayer"/> using cell coordinates</summary>
+		public T this[CPos cell]
+		{
+			get
+			{
+				return entries[Index(cell)];
+			}
+
+			set
+			{
+				entries[Index(cell)] = value;
+			}
+		}
+
+		/// <summary>Gets or sets the layer contents using raw map coordinates (not CPos!)</summary>
+		public T this[int u, int v]
+		{
+			get
+			{
+				return entries[v * Size.Width + u];
+			}
+
+			set
+			{
+				entries[v * Size.Width + u] = value;
+			}
+		}
+
+		/// <summary>Clears the layer contents with a known value</summary>
+		public void Clear(T clearValue)
+		{
+			for (var i = 0; i < entries.Length; i++)
+				entries[i] = clearValue;
+		}
+
+		public IEnumerator<T> GetEnumerator()
+		{
+			return (IEnumerator<T>)entries.GetEnumerator();
+		}
+
+		IEnumerator IEnumerable.GetEnumerator()
+		{
+			return GetEnumerator();
+		}
+	}
+
+	// Helper functions
+	public static class CellLayer
+	{
+		/// <summary>Create a new layer by resizing another layer.  New cells are filled with defaultValue.</summary>
+		public static CellLayer<T> Resize<T>(CellLayer<T> layer, Size newSize, T defaultValue)
+		{
+			var result = new CellLayer<T>(newSize);
+			var width = Math.Min(layer.Size.Width, newSize.Width);
+			var height = Math.Min(layer.Size.Height, newSize.Height);
+
+			result.Clear(defaultValue);
+			for (var j = 0; j < height; j++)
+				for (var i = 0; i < width; i++)
+					result[i, j] = layer[i, j];
+
+			return result;
+		}
+	}
+}
diff --git a/OpenRA.Game/Map/CellRegion.cs b/OpenRA.Game/Map/CellRegion.cs
new file mode 100644
index 0000000000..3cdccc7fbe
--- /dev/null
+++ b/OpenRA.Game/Map/CellRegion.cs
@@ -0,0 +1,101 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation. For more information,
+ * see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Drawing;
+using OpenRA.Graphics;
+
+namespace OpenRA
+{
+	// Represents a (on-screen) rectangular collection of tiles.
+	// TopLeft and BottomRight are inclusive
+	public class CellRegion : IEnumerable<CPos>
+	{
+		// Corners of the region
+		public readonly CPos TopLeft;
+		public readonly CPos BottomRight;
+
+		// Corners in map coordinates
+		// Defined for forward compatibility with diagonal cell grids
+		readonly CPos mapTopLeft;
+		readonly CPos mapBottomRight;
+
+		public CellRegion(CPos topLeft, CPos bottomRight)
+		{
+			TopLeft = topLeft;
+			BottomRight = bottomRight;
+
+			mapTopLeft = TopLeft;
+			mapBottomRight = BottomRight;
+		}
+
+		public bool Contains(CPos cell)
+		{
+			// Defined for forward compatibility with diagonal cell grids
+			var uv = cell;
+			return uv.X >= mapTopLeft.X && uv.X <= mapBottomRight.X && uv.Y >= mapTopLeft.Y && uv.Y <= mapBottomRight.Y;
+		}
+
+		public IEnumerator<CPos> GetEnumerator()
+		{
+			return new CellRegionEnumerator(this);
+		}
+
+		IEnumerator IEnumerable.GetEnumerator()
+		{
+			return GetEnumerator();
+		}
+
+		class CellRegionEnumerator : IEnumerator<CPos>
+		{
+			readonly CellRegion r;
+
+			// Current position, in map coordinates
+			int u, v;
+
+			public CellRegionEnumerator(CellRegion region)
+			{
+				r = region;
+				Reset();
+			}
+
+			public bool MoveNext()
+			{
+				u += 1;
+
+				// Check for column overflow
+				if (u > r.mapBottomRight.X)
+				{
+					v += 1;
+					u = r.mapTopLeft.X;
+
+					// Check for row overflow
+					if (v > r.mapBottomRight.Y)
+						return false;
+				}
+
+				return true;
+			}
+
+			public void Reset()
+			{
+				// Enumerator starts *before* the first element in the sequence.
+				u = r.mapTopLeft.X - 1;
+				v = r.mapTopLeft.Y;
+			}
+
+			public CPos Current { get { return new CPos(u, v); } }
+			object IEnumerator.Current { get { return Current; } }
+			public void Dispose() { }
+		}
+	}
+}
diff --git a/OpenRA.Game/Map/Map.cs b/OpenRA.Game/Map/Map.cs
index 01f5685963..06f3b9019d 100644
--- a/OpenRA.Game/Map/Map.cs
+++ b/OpenRA.Game/Map/Map.cs
@@ -9,6 +9,7 @@
 #endregion
 
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Drawing;
 using System.IO;
@@ -110,29 +111,38 @@ namespace OpenRA
 		[FieldLoader.Ignore] public byte TileFormat = 1;
 		public int2 MapSize;
 
-		[FieldLoader.Ignore] public Lazy<TileReference<ushort, byte>[,]> MapTiles;
-		[FieldLoader.Ignore] public Lazy<TileReference<byte, byte>[,]> MapResources;
-		[FieldLoader.Ignore] public int[,] CustomTerrain;
+		[FieldLoader.Ignore] public Lazy<CellLayer<TerrainTile>> MapTiles;
+		[FieldLoader.Ignore] public Lazy<CellLayer<ResourceTile>> MapResources;
+		[FieldLoader.Ignore] public CellLayer<int> CustomTerrain;
 
 		[FieldLoader.Ignore] Lazy<Ruleset> rules;
 		public Ruleset Rules { get { return rules != null ? rules.Value : null; } }
 		public SequenceProvider SequenceProvider { get { return Rules.Sequences[Tileset]; } }
 
+		[FieldLoader.Ignore] public CellRegion Cells;
+
 		public static Map FromTileset(TileSet tileset)
 		{
-			var tile = tileset.Templates.First();
-			var tileRef = new TileReference<ushort, byte> { Type = tile.Key, Index = (byte)0 };
+			var size = new Size(1, 1);
+			var tileRef = new TerrainTile(tileset.Templates.First().Key, (byte)0);
+
+			var makeMapTiles =  Exts.Lazy(() =>
+			{
+				var ret = new CellLayer<TerrainTile>(size);
+				ret.Clear(tileRef);
+				return ret;
+			});
 
 			var map = new Map()
 			{
 				Title = "Name your map here",
 				Description = "Describe your map here",
 				Author = "Your name here",
-				MapSize = new int2(1, 1),
+				MapSize = new int2(size),
 				Tileset = tileset.Id,
 				Options = new MapOptions(),
-				MapResources = Exts.Lazy(() => new TileReference<byte, byte>[1, 1]),
-				MapTiles = Exts.Lazy(() => new TileReference<ushort, byte>[1, 1] { { tileRef } }),
+				MapResources = Exts.Lazy(() => new CellLayer<ResourceTile>(size)),
+				MapTiles = makeMapTiles,
 				Actors = Exts.Lazy(() => new Dictionary<string, ActorReference>()),
 				Smudges = Exts.Lazy(() => new List<SmudgeReference>())
 			};
@@ -229,11 +239,6 @@ namespace OpenRA
 			NotificationDefinitions = MiniYaml.NodesOrEmpty(yaml, "Notifications");
 			TranslationDefinitions = MiniYaml.NodesOrEmpty(yaml, "Translations");
 
-			CustomTerrain = new int[MapSize.X, MapSize.Y];
-			for (var x = 0; x < MapSize.X; x++)
-				for (var y = 0; y < MapSize.Y; y++)
-					CustomTerrain[x, y] = -1;
-
 			MapTiles = Exts.Lazy(() => LoadMapTiles());
 			MapResources = Exts.Lazy(() => LoadResourceTiles());
 
@@ -254,6 +259,14 @@ namespace OpenRA
 		void PostInit()
 		{
 			rules = Exts.Lazy(() => Game.modData.RulesetCache.LoadMapRules(this));
+
+			var tl = new CPos(Bounds.Left, Bounds.Top);
+			var br = new CPos(Bounds.Right - 1, Bounds.Bottom - 1);
+			Cells = new CellRegion(tl, br);
+
+			CustomTerrain = new CellLayer<int>(this);
+			foreach (var cell in Cells)
+				CustomTerrain[cell] = -1;
 		}
 
 		public Ruleset PreloadRules()
@@ -346,9 +359,9 @@ namespace OpenRA
 			Container.Write(entries);
 		}
 
-		public TileReference<ushort, byte>[,] LoadMapTiles()
+		public CellLayer<TerrainTile> LoadMapTiles()
 		{
-			var tiles = new TileReference<ushort, byte>[MapSize.X, MapSize.Y];
+			var tiles = new CellLayer<TerrainTile>(this);
 			using (var dataStream = Container.GetContent("map.bin"))
 			{
 				if (dataStream.ReadUInt8() != 1)
@@ -365,23 +378,27 @@ namespace OpenRA
 				var data = dataStream.ReadBytes(MapSize.X * MapSize.Y * 3);
 				var d = 0;
 				for (var i = 0; i < MapSize.X; i++)
+				{
 					for (var j = 0; j < MapSize.Y; j++)
 					{
 						var tile = BitConverter.ToUInt16(data, d);
 						d += 2;
+
 						var index = data[d++];
 						if (index == byte.MaxValue)
 							index = (byte)(i % 4 + (j % 4) * 4);
-						tiles[i, j] = new TileReference<ushort, byte>(tile, index);
+
+						tiles[i, j] = new TerrainTile(tile, index);
 					}
+				}
 			}
 
 			return tiles;
 		}
 
-		public TileReference<byte, byte>[,] LoadResourceTiles()
+		public CellLayer<ResourceTile> LoadResourceTiles()
 		{
-			var resources = new TileReference<byte, byte>[MapSize.X, MapSize.Y];
+			var resources = new CellLayer<ResourceTile>(this);
 
 			using (var dataStream = Container.GetContent("map.bin"))
 			{
@@ -400,10 +417,11 @@ namespace OpenRA
 
 				var data = dataStream.ReadBytes(MapSize.X * MapSize.Y * 2);
 				var d = 0;
+
 				// Load resource data
 				for (var i = 0; i < MapSize.X; i++)
 					for (var j = 0; j < MapSize.Y; j++)
-						resources[i, j] = new TileReference<byte, byte>(data[d++], data[d++]);
+						resources[i, j] = new ResourceTile(data[d++], data[d++]);
 			}
 
 			return resources;
@@ -423,38 +441,43 @@ namespace OpenRA
 				for (var i = 0; i < MapSize.X; i++)
 					for (var j = 0; j < MapSize.Y; j++)
 					{
-						writer.Write(MapTiles.Value[i, j].Type);
-						writer.Write(MapTiles.Value[i, j].Index);
+						var tile = MapTiles.Value[new CPos(i, j)];
+						writer.Write(tile.Type);
+						writer.Write(tile.Index);
 					}
 
 				// Resource data
 				for (var i = 0; i < MapSize.X; i++)
+				{
 					for (var j = 0; j < MapSize.Y; j++)
 					{
-						writer.Write(MapResources.Value[i, j].Type);
-						writer.Write(MapResources.Value[i, j].Index);
+						var tile = MapResources.Value[new CPos(i, j)];
+						writer.Write(tile.Type);
+						writer.Write(tile.Index);
 					}
+				}
 			}
 
 			return dataStream.ToArray();
 		}
 
-		public bool IsInMap(CPos xy) { return IsInMap(xy.X, xy.Y); }
-		public bool IsInMap(int x, int y) { return Bounds.Contains(x, y); }
+		public bool Contains(CPos xy) { return Bounds.Contains(xy.X, xy.Y); }
 
 		public void Resize(int width, int height)		// editor magic.
 		{
 			var oldMapTiles = MapTiles.Value;
 			var oldMapResources = MapResources.Value;
+			var newSize = new Size(width, height);
 
-			MapTiles = Exts.Lazy(() => Exts.ResizeArray(oldMapTiles, oldMapTiles[0, 0], width, height));
-			MapResources = Exts.Lazy(() => Exts.ResizeArray(oldMapResources, oldMapResources[0, 0], width, height));
-			MapSize = new int2(width, height);
+			MapTiles = Exts.Lazy(() => CellLayer.Resize(oldMapTiles, newSize, oldMapTiles[0, 0]));
+			MapResources = Exts.Lazy(() => CellLayer.Resize(oldMapResources, newSize, oldMapResources[0, 0]));
+			MapSize = new int2(newSize);
 		}
 
 		public void ResizeCordon(int left, int top, int right, int bottom)
 		{
 			Bounds = Rectangle.FromLTRB(left, top, right, bottom);
+			Cells = new CellRegion(new CPos(Bounds.Left, Bounds.Top), new CPos(Bounds.Right - 1, Bounds.Bottom - 1));
 		}
 
 		string ComputeHash()
@@ -524,26 +547,30 @@ namespace OpenRA
 			{
 				for (var i = Bounds.Left; i < Bounds.Right; i++)
 				{
-					var tr = MapTiles.Value[i, j];
-					if (!tileset.Templates.ContainsKey(tr.Type))
+					var cell = new CPos(i, j);
+					var type = MapTiles.Value[cell].Type;
+					var index = MapTiles.Value[cell].Index;
+					if (!tileset.Templates.ContainsKey(type))
 					{
-						Console.WriteLine("Unknown Tile ID {0}".F(tr.Type));
+						Console.WriteLine("Unknown Tile ID {0}".F(type));
 						continue;
 					}
-					var template = tileset.Templates[tr.Type];
+
+					var template = tileset.Templates[type];
 					if (!template.PickAny)
 						continue;
-					tr.Index = (byte)r.Next(0, template.TilesCount);
-					MapTiles.Value[i, j] = tr;
+
+					index = (byte)r.Next(0, template.TilesCount);
+					MapTiles.Value[cell] = new TerrainTile(type, index);
 				}
 			}
 		}
 
 		public int GetTerrainIndex(CPos cell)
 		{
-			var custom = CustomTerrain[cell.X, cell.Y];
+			var custom = CustomTerrain[cell];
 			var tileSet = Rules.TileSets[Tileset];
-			return custom != -1 ? custom : tileSet.GetTerrainIndex(MapTiles.Value[cell.X, cell.Y]);
+			return custom != -1 ? custom : tileSet.GetTerrainIndex(MapTiles.Value[cell]);
 		}
 
 		public TerrainTypeInfo GetTerrainInfo(CPos cell)
@@ -606,12 +633,12 @@ namespace OpenRA
 			if (range >= TilesByDistance.Length)
 				throw new InvalidOperationException("FindTilesInCircle supports queries for only <= {0}".F(MaxTilesInCircleRange));
 
-			for(var i = 0; i <= range; i++)
+			for (var i = 0; i <= range; i++)
 			{
-				foreach(var offset in TilesByDistance[i])
+				foreach (var offset in TilesByDistance[i])
 				{
 					var t = offset + center;
-					if (Bounds.Contains(t.X, t.Y))
+					if (Contains(t))
 						yield return t;
 				}
 			}
diff --git a/OpenRA.Game/Map/TileReference.cs b/OpenRA.Game/Map/TileReference.cs
index 5dc7d719b8..1d835888a5 100644
--- a/OpenRA.Game/Map/TileReference.cs
+++ b/OpenRA.Game/Map/TileReference.cs
@@ -10,15 +10,29 @@
 
 namespace OpenRA
 {
-	public struct TileReference<T, U>
+	public struct TerrainTile
 	{
-		public T Type;
-		public U Index;
+		public readonly ushort Type;
+		public readonly byte Index;
 
-		public TileReference(T t, U i)
+		public TerrainTile(ushort type, byte index)
 		{
-			Type = t;
-			Index = i;
+			Type = type;
+			Index = index;
+		}
+
+		public override int GetHashCode() { return Type.GetHashCode() ^ Index.GetHashCode(); }
+	}
+
+	public struct ResourceTile
+	{
+		public readonly byte Type;
+		public readonly byte Index;
+
+		public ResourceTile(byte type, byte index)
+		{
+			Type = type;
+			Index = index;
 		}
 
 		public override int GetHashCode() { return Type.GetHashCode() ^ Index.GetHashCode(); }
diff --git a/OpenRA.Game/Map/TileSet.cs b/OpenRA.Game/Map/TileSet.cs
index 1397cd5eea..1afa545d16 100644
--- a/OpenRA.Game/Map/TileSet.cs
+++ b/OpenRA.Game/Map/TileSet.cs
@@ -223,7 +223,7 @@ namespace OpenRA
 			throw new InvalidDataException("Tileset '{0}' lacks terrain type '{1}'".F(Id, type));
 		}
 
-		public int GetTerrainIndex(TileReference<ushort, byte> r)
+		public int GetTerrainIndex(TerrainTile r)
 		{
 			var tpl = Templates[r.Type];
 
@@ -261,7 +261,7 @@ namespace OpenRA
 			root.WriteToFile(filepath);
 		}
 
-		public TerrainTypeInfo GetTerrainInfo(TileReference<ushort, byte> r)
+		public TerrainTypeInfo GetTerrainInfo(TerrainTile r)
 		{
 			return terrainInfo[GetTerrainIndex(r)];
 		}
diff --git a/OpenRA.Game/OpenRA.Game.csproj b/OpenRA.Game/OpenRA.Game.csproj
index 0657df79df..d41cd7a7c4 100644
--- a/OpenRA.Game/OpenRA.Game.csproj
+++ b/OpenRA.Game/OpenRA.Game.csproj
@@ -235,6 +235,8 @@
     <Compile Include="Support\MersenneTwister.cs" />
     <Compile Include="GameInformation.cs" />
     <Compile Include="Widgets\RootWidget.cs" />
+    <Compile Include="Map\CellLayer.cs" />
+    <Compile Include="Map\CellRegion.cs" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="FileSystem\D2kSoundResources.cs" />
@@ -358,4 +360,4 @@
   </Target>
   -->
   <ItemGroup />
-</Project>
\ No newline at end of file
+</Project>
diff --git a/OpenRA.Game/Orders/GenericSelectTarget.cs b/OpenRA.Game/Orders/GenericSelectTarget.cs
index c1499d18d2..a6048754ca 100644
--- a/OpenRA.Game/Orders/GenericSelectTarget.cs
+++ b/OpenRA.Game/Orders/GenericSelectTarget.cs
@@ -55,7 +55,7 @@ namespace OpenRA.Orders
 
 		IEnumerable<Order> OrderInner(World world, CPos xy, MouseInput mi)
 		{
-			if (mi.Button == expectedButton && world.Map.IsInMap(xy))
+			if (mi.Button == expectedButton && world.Map.Contains(xy))
 			{
 				world.CancelInputMode();
 				foreach (var subject in subjects)
@@ -66,6 +66,6 @@ namespace OpenRA.Orders
 		public virtual void Tick(World world) { }
 		public IEnumerable<IRenderable> Render(WorldRenderer wr, World world) { yield break; }
 		public void RenderAfterWorld(WorldRenderer wr, World world) { }
-		public string GetCursor(World world, CPos xy, MouseInput mi) { return world.Map.IsInMap(xy) ? cursor : "generic-blocked"; }
+		public string GetCursor(World world, CPos xy, MouseInput mi) { return world.Map.Contains(xy) ? cursor : "generic-blocked"; }
 	}
 }
diff --git a/OpenRA.Game/Traits/World/ActorMap.cs b/OpenRA.Game/Traits/World/ActorMap.cs
index c85de0c256..fd28f527c2 100644
--- a/OpenRA.Game/Traits/World/ActorMap.cs
+++ b/OpenRA.Game/Traits/World/ActorMap.cs
@@ -41,7 +41,7 @@ namespace OpenRA.Traits
 
 		readonly ActorMapInfo info;
 		readonly Map map;
-		InfluenceNode[,] influence;
+		readonly CellLayer<InfluenceNode> influence;
 
 		List<Actor>[] actors;
 		int rows, cols;
@@ -56,7 +56,7 @@ namespace OpenRA.Traits
 		{
 			this.info = info;
 			map = world.Map;
-			influence = new InfluenceNode[world.Map.MapSize.X, world.Map.MapSize.Y];
+			influence = new CellLayer<InfluenceNode>(world.Map);
 
 			cols = world.Map.MapSize.X / info.BinSize + 1;
 			rows = world.Map.MapSize.Y / info.BinSize + 1;
@@ -71,20 +71,20 @@ namespace OpenRA.Traits
 
 		public IEnumerable<Actor> GetUnitsAt(CPos a)
 		{
-			if (!map.IsInMap(a))
+			if (!map.Contains(a))
 				yield break;
 
-			for (var i = influence[a.X, a.Y]; i != null; i = i.Next)
+			for (var i = influence[a]; i != null; i = i.Next)
 				if (!i.Actor.Destroyed)
 					yield return i.Actor;
 		}
 
 		public IEnumerable<Actor> GetUnitsAt(CPos a, SubCell sub)
 		{
-			if (!map.IsInMap(a))
+			if (!map.Contains(a))
 				yield break;
 
-			for (var i = influence[a.X, a.Y]; i != null; i = i.Next)
+			for (var i = influence[a]; i != null; i = i.Next)
 				if (!i.Actor.Destroyed && (i.SubCell == sub || i.SubCell == SubCell.FullCell))
 					yield return i.Actor;
 		}
@@ -107,12 +107,12 @@ namespace OpenRA.Traits
 
 		public bool AnyUnitsAt(CPos a)
 		{
-			return influence[a.X, a.Y] != null;
+			return influence[a] != null;
 		}
 
 		public bool AnyUnitsAt(CPos a, SubCell sub)
 		{
-			for (var i = influence[a.X, a.Y]; i != null; i = i.Next)
+			for (var i = influence[a]; i != null; i = i.Next)
 				if (i.SubCell == sub || i.SubCell == SubCell.FullCell)
 					return true;
 
@@ -122,20 +122,25 @@ namespace OpenRA.Traits
 		public void AddInfluence(Actor self, IOccupySpace ios)
 		{
 			foreach (var c in ios.OccupiedCells())
-				influence[c.First.X, c.First.Y] = new InfluenceNode { Next = influence[c.First.X, c.First.Y], SubCell = c.Second, Actor = self };
+				influence[c.First] = new InfluenceNode { Next = influence[c.First], SubCell = c.Second, Actor = self };
 		}
 
 		public void RemoveInfluence(Actor self, IOccupySpace ios)
 		{
 			foreach (var c in ios.OccupiedCells())
-				RemoveInfluenceInner(ref influence[c.First.X, c.First.Y], self);
+			{
+				var temp = influence[c.First];
+				RemoveInfluenceInner(ref temp, self);
+				influence[c.First] = temp;
+			}
 		}
 
 		void RemoveInfluenceInner(ref InfluenceNode influenceNode, Actor toRemove)
 		{
 			if (influenceNode == null)
 				return;
-			else if (influenceNode.Actor == toRemove)
+
+			if (influenceNode.Actor == toRemove)
 				influenceNode = influenceNode.Next;
 
 			if (influenceNode != null)
@@ -206,5 +211,11 @@ namespace OpenRA.Traits
 				}
 			}
 		}
+
+		public IEnumerable<Actor> ActorsInWorld()
+		{
+			return actors.SelectMany(a => a.Where(b => b.IsInWorld))
+				.Distinct();
+		}
 	}
 }
diff --git a/OpenRA.Game/Traits/World/ResourceLayer.cs b/OpenRA.Game/Traits/World/ResourceLayer.cs
index 1efc612ddc..0f405e1931 100644
--- a/OpenRA.Game/Traits/World/ResourceLayer.cs
+++ b/OpenRA.Game/Traits/World/ResourceLayer.cs
@@ -22,89 +22,78 @@ namespace OpenRA.Traits
 		static readonly CellContents EmptyCell = new CellContents();
 
 		World world;
-		protected CellContents[,] content;
-		protected CellContents[,] render;
+		protected CellLayer<CellContents> content;
+		protected CellLayer<CellContents> render;
 		List<CPos> dirty;
 
 		public void Render(WorldRenderer wr)
 		{
-			var clip = wr.Viewport.CellBounds;
-			for (var x = clip.Left; x < clip.Right; x++)
+			foreach (var cell in wr.Viewport.VisibleCells)
 			{
-				for (var y = clip.Top; y < clip.Bottom; y++)
-				{
-					var pos = new CPos(x, y);
-					if (world.ShroudObscures(pos))
-						continue;
+				if (world.ShroudObscures(cell))
+					continue;
 
-					var c = render[x, y];
-					if (c.Sprite != null)
-						new SpriteRenderable(c.Sprite, pos.CenterPosition,
-							WVec.Zero, -511, c.Type.Palette, 1f, true).Render(wr);
-				}
+				var c = render[cell];
+				if (c.Sprite != null)
+					new SpriteRenderable(c.Sprite, cell.CenterPosition,
+						WVec.Zero, -511, c.Type.Palette, 1f, true).Render(wr);
 			}
 		}
 
-		int GetAdjacentCellsWith(ResourceType t, int i, int j)
+		int GetAdjacentCellsWith(ResourceType t, CPos cell)
 		{
 			var sum = 0;
 			for (var u = -1; u < 2; u++)
 				for (var v = -1; v < 2; v++)
-					if (content[i + u, j + v].Type == t)
+					if (content[cell + new CVec(u, v)].Type == t)
 						++sum;
+
 			return sum;
 		}
 
 		public void WorldLoaded(World w, WorldRenderer wr)
 		{
 			this.world = w;
-			content = new CellContents[w.Map.MapSize.X, w.Map.MapSize.Y];
-			render = new CellContents[w.Map.MapSize.X, w.Map.MapSize.Y];
+			content = new CellLayer<CellContents>(w.Map);
+			render = new CellLayer<CellContents>(w.Map);
 			dirty = new List<CPos>();
 
 			var resources = w.WorldActor.TraitsImplementing<ResourceType>()
 				.ToDictionary(r => r.Info.ResourceType, r => r);
 
-			var map = w.Map;
-			for (var x = map.Bounds.Left; x < map.Bounds.Right; x++)
+			foreach (var cell in w.Map.Cells)
 			{
-				for (var y = map.Bounds.Top; y < map.Bounds.Bottom; y++)
-				{
-					var cell = new CPos(x, y);
-					ResourceType t;
-					if (!resources.TryGetValue(w.Map.MapResources.Value[x, y].Type, out t))
-						continue;
+				ResourceType t;
+				if (!resources.TryGetValue(w.Map.MapResources.Value[cell].Type, out t))
+					continue;
 
-					if (!AllowResourceAt(t, cell))
-						continue;
+				if (!AllowResourceAt(t, cell))
+					continue;
 
-					content[x, y] = CreateResourceCell(t, cell);
-				}
+				content[cell] = CreateResourceCell(t, cell);
 			}
 
 			// Set initial density based on the number of neighboring resources
-			for (var x = map.Bounds.Left; x < map.Bounds.Right; x++)
+			foreach (var cell in w.Map.Cells)
 			{
-				for (var y = map.Bounds.Top; y < map.Bounds.Bottom; y++)
+				var type = content[cell].Type;
+				if (type != null)
 				{
-					var type = content[x, y].Type;
-					if (type != null)
-					{
-						// Adjacent includes the current cell, so is always >= 1
-						var adjacent = GetAdjacentCellsWith(type, x, y);
-						var density = int2.Lerp(0, type.Info.MaxDensity, adjacent, 9);
-						content[x, y].Density = Math.Max(density, 1);
+					// Adjacent includes the current cell, so is always >= 1
+					var adjacent = GetAdjacentCellsWith(type, cell);
+					var density = int2.Lerp(0, type.Info.MaxDensity, adjacent, 9);
+					var temp = content[cell];
+					temp.Density = Math.Max(density, 1);
 
-						render[x, y] = content[x, y];
-						UpdateRenderedSprite(new CPos(x, y));
-					}
+					render[cell] = content[cell] = temp;
+					UpdateRenderedSprite(cell);
 				}
 			}
 		}
 
-		protected virtual void UpdateRenderedSprite(CPos p)
+		protected virtual void UpdateRenderedSprite(CPos cell)
 		{
-			var t = render[p.X, p.Y];
+			var t = render[cell];
 			if (t.Density > 0)
 			{
 				var sprites = t.Type.Variants[t.Variant];
@@ -114,7 +103,7 @@ namespace OpenRA.Traits
 			else
 				t.Sprite = null;
 
-			render[p.X, p.Y] = t;
+			render[cell] = t;
 		}
 
 		protected virtual string ChooseRandomVariant(ResourceType t)
@@ -129,7 +118,7 @@ namespace OpenRA.Traits
 			{
 				if (!self.World.FogObscures(c))
 				{
-					render[c.X, c.Y] = content[c.X, c.Y];
+					render[c] = content[c];
 					UpdateRenderedSprite(c);
 					remove.Add(c);
 				}
@@ -139,15 +128,15 @@ namespace OpenRA.Traits
 				dirty.Remove(r);
 		}
 
-		public bool AllowResourceAt(ResourceType rt, CPos a)
+		public bool AllowResourceAt(ResourceType rt, CPos cell)
 		{
-			if (!world.Map.IsInMap(a.X, a.Y))
+			if (!world.Map.Contains(cell))
 				return false;
 
-			if (!rt.Info.AllowedTerrainTypes.Contains(world.Map.GetTerrainInfo(a).Type))
+			if (!rt.Info.AllowedTerrainTypes.Contains(world.Map.GetTerrainInfo(cell).Type))
 				return false;
 
-			if (!rt.Info.AllowUnderActors && world.ActorMap.AnyUnitsAt(a))
+			if (!rt.Info.AllowUnderActors && world.ActorMap.AnyUnitsAt(cell))
 				return false;
 
 			return true;
@@ -160,9 +149,10 @@ namespace OpenRA.Traits
 				|| (currentResourceType == null && AllowResourceAt(newResourceType, cell));
 		}
 
-		CellContents CreateResourceCell(ResourceType t, CPos p)
+		CellContents CreateResourceCell(ResourceType t, CPos cell)
 		{
-			world.Map.CustomTerrain[p.X, p.Y] = world.TileSet.GetTerrainIndex(t.Info.TerrainType);
+			world.Map.CustomTerrain[cell] = world.TileSet.GetTerrainIndex(t.Info.TerrainType);
+
 			return new CellContents
 			{
 				Type = t,
@@ -172,7 +162,7 @@ namespace OpenRA.Traits
 
 		public void AddResource(ResourceType t, CPos p, int n)
 		{
-			var cell = content[p.X, p.Y];
+			var cell = content[p];
 			if (cell.Type == null)
 				cell = CreateResourceCell(t, p);
 
@@ -180,58 +170,60 @@ namespace OpenRA.Traits
 				return;
 
 			cell.Density = Math.Min(cell.Type.Info.MaxDensity, cell.Density + n);
-			content[p.X, p.Y] = cell;
+			content[p] = cell;
 
 			if (!dirty.Contains(p))
 				dirty.Add(p);
 		}
 
-		public bool IsFull(CPos c)
+		public bool IsFull(CPos cell)
 		{
-			return content[c.X, c.Y].Density == content[c.X, c.Y].Type.Info.MaxDensity;
+			return content[cell].Density == content[cell].Type.Info.MaxDensity;
 		}
 
-		public ResourceType Harvest(CPos p)
+		public ResourceType Harvest(CPos cell)
 		{
-			var type = content[p.X, p.Y].Type;
-			if (type == null)
+			var c = content[cell];
+			if (c.Type == null)
 				return null;
 
-			if (--content[p.X, p.Y].Density < 0)
+			if (--c.Density < 0)
 			{
-				content[p.X, p.Y] = EmptyCell;
-				world.Map.CustomTerrain[p.X, p.Y] = -1;
+				content[cell] = EmptyCell;
+				world.Map.CustomTerrain[cell] = -1;
 			}
+			else
+				content[cell] = c;
 
-			if (!dirty.Contains(p))
-				dirty.Add(p);
+			if (!dirty.Contains(cell))
+				dirty.Add(cell);
 
-			return type;
+			return c.Type;
 		}
 
-		public void Destroy(CPos p)
+		public void Destroy(CPos cell)
 		{
 			// Don't break other users of CustomTerrain if there are no resources
-			if (content[p.X, p.Y].Type == null)
+			if (content[cell].Type == null)
 				return;
 
 			// Clear cell
-			content[p.X, p.Y] = EmptyCell;
-			world.Map.CustomTerrain[p.X, p.Y] = -1;
+			content[cell] = EmptyCell;
+			world.Map.CustomTerrain[cell] = -1;
 
-			if (!dirty.Contains(p))
-				dirty.Add(p);
+			if (!dirty.Contains(cell))
+				dirty.Add(cell);
 		}
 
-		public ResourceType GetResource(CPos p) { return content[p.X, p.Y].Type; }
-		public ResourceType GetRenderedResource(CPos p) { return render[p.X, p.Y].Type; }
-		public int GetResourceDensity(CPos p) { return content[p.X, p.Y].Density; }
-		public int GetMaxResourceDensity(CPos p)
+		public ResourceType GetResource(CPos cell) { return content[cell].Type; }
+		public ResourceType GetRenderedResource(CPos cell) { return render[cell].Type; }
+		public int GetResourceDensity(CPos cell) { return content[cell].Density; }
+		public int GetMaxResourceDensity(CPos cell)
 		{
-			if (content[p.X, p.Y].Type == null)
+			if (content[cell].Type == null)
 				return 0;
 
-			return content[p.X, p.Y].Type.Info.MaxDensity;
+			return content[cell].Type.Info.MaxDensity;
 		}
 
 		public struct CellContents
diff --git a/OpenRA.Game/Traits/World/Shroud.cs b/OpenRA.Game/Traits/World/Shroud.cs
index c4804e535e..154dc66384 100644
--- a/OpenRA.Game/Traits/World/Shroud.cs
+++ b/OpenRA.Game/Traits/World/Shroud.cs
@@ -27,9 +27,9 @@ namespace OpenRA.Traits
 		Actor self;
 		Map map;
 
-		int[,] visibleCount;
-		int[,] generatedShroudCount;
-		bool[,] explored;
+		CellLayer<int> visibleCount;
+		CellLayer<int> generatedShroudCount;
+		CellLayer<bool> explored;
 
 		readonly Lazy<IFogVisibilityModifier[]> fogVisibilities;
 
@@ -38,8 +38,6 @@ namespace OpenRA.Traits
 		Dictionary<Actor, CPos[]> visibility = new Dictionary<Actor, CPos[]>();
 		Dictionary<Actor, CPos[]> generation = new Dictionary<Actor, CPos[]>();
 
-		public Rectangle ExploredBounds { get; private set; }
-
 		public int Hash { get; private set; }
 
 		public Shroud(Actor self)
@@ -47,9 +45,9 @@ namespace OpenRA.Traits
 			this.self = self;
 			map = self.World.Map;
 
-			visibleCount = new int[map.MapSize.X, map.MapSize.Y];
-			generatedShroudCount = new int[map.MapSize.X, map.MapSize.Y];
-			explored = new bool[map.MapSize.X, map.MapSize.Y];
+			visibleCount = new CellLayer<int>(map);
+			generatedShroudCount = new CellLayer<int>(map);
+			explored = new CellLayer<bool>(map);
 
 			self.World.ActorAdded += AddVisibility;
 			self.World.ActorRemoved += RemoveVisibility;
@@ -57,9 +55,6 @@ namespace OpenRA.Traits
 			self.World.ActorAdded += AddShroudGeneration;
 			self.World.ActorRemoved += RemoveShroudGeneration;
 
-			if (!self.World.LobbyInfo.GlobalSettings.Shroud)
-				ExploredBounds = map.Bounds;
-
 			fogVisibilities = Exts.Lazy(() => self.TraitsImplementing<IFogVisibilityModifier>().ToArray());
 		}
 
@@ -71,15 +66,12 @@ namespace OpenRA.Traits
 		static IEnumerable<CPos> FindVisibleTiles(World world, CPos position, WRange radius)
 		{
 			var r = (radius.Range + 1023) / 1024;
-			var min = (position - new CVec(r, r)).Clamp(world.Map.Bounds);
-			var max = (position + new CVec(r, r)).Clamp(world.Map.Bounds);
-
-			var circleArea = radius.Range * radius.Range;
+			var limit = radius.Range * radius.Range;
 			var pos = position.CenterPosition;
-			for (var j = min.Y; j <= max.Y; j++)
-				for (var i = min.X; i <= max.X; i++)
-					if (circleArea >= (new CPos(i, j).CenterPosition - pos).LengthSquared)
-						yield return new CPos(i, j);
+
+			foreach (var cell in world.Map.FindTilesInCircle(position, r))
+				if ((cell.CenterPosition - pos).HorizontalLengthSquared <= limit)
+					yield return cell;
 		}
 
 		void AddVisibility(Actor a)
@@ -92,20 +84,11 @@ namespace OpenRA.Traits
 			var visible = origins.SelectMany(o => FindVisibleTiles(a.World, o, rs.Range))
 				.Distinct().ToArray();
 
-			// Update bounding rect
-			var r = (rs.Range.Range + 1023) / 1024;
-
-			foreach (var o in origins)
-			{
-				var box = new Rectangle(o.X - r, o.Y - r, 2 * r + 1, 2 * r + 1);
-				ExploredBounds = Rectangle.Union(ExploredBounds, box);
-			}
-
 			// Update visibility
 			foreach (var c in visible)
 			{
-				visibleCount[c.X, c.Y]++;
-				explored[c.X, c.Y] = true;
+				visibleCount[c]++;
+				explored[c] = true;
 			}
 
 			if (visibility.ContainsKey(a))
@@ -122,7 +105,7 @@ namespace OpenRA.Traits
 				return;
 
 			foreach (var c in visible)
-				visibleCount[c.X, c.Y]--;
+				visibleCount[c]--;
 
 			visibility.Remove(a);
 			Invalidate();
@@ -147,7 +130,7 @@ namespace OpenRA.Traits
 			var shrouded = GetVisOrigins(a).SelectMany(o => FindVisibleTiles(a.World, o, cs.Range))
 				.Distinct().ToArray();
 			foreach (var c in shrouded)
-				generatedShroudCount[c.X, c.Y]++;
+				generatedShroudCount[c]++;
 
 			if (generation.ContainsKey(a))
 				throw new InvalidOperationException("Attempting to add duplicate shroud generation");
@@ -163,7 +146,7 @@ namespace OpenRA.Traits
 				return;
 
 			foreach (var c in shrouded)
-				generatedShroudCount[c.X, c.Y]--;
+				generatedShroudCount[c]--;
 
 			generation.Remove(a);
 			Invalidate();
@@ -203,55 +186,44 @@ namespace OpenRA.Traits
 		public void Explore(World world, CPos center, WRange range)
 		{
 			foreach (var q in FindVisibleTiles(world, center, range))
-				explored[q.X, q.Y] = true;
-
-			var r = (range.Range + 1023) / 1024;
-			var box = new Rectangle(center.X - r, center.Y - r, 2 * r + 1, 2 * r + 1);
-			ExploredBounds = Rectangle.Union(ExploredBounds, box);
+				explored[q] = true;
 
 			Invalidate();
 		}
 
 		public void Explore(Shroud s)
 		{
-			for (var i = map.Bounds.Left; i < map.Bounds.Right; i++)
-				for (var j = map.Bounds.Top; j < map.Bounds.Bottom; j++)
-					if (s.explored[i,j] == true)
-						explored[i, j] = true;
+			foreach (var cell in map.Cells)
+				if (s.explored[cell])
+					explored[cell] = true;
 
-			ExploredBounds = Rectangle.Union(ExploredBounds, s.ExploredBounds);
+			Invalidate();
 		}
 
 		public void ExploreAll(World world)
 		{
-			for (var i = map.Bounds.Left; i < map.Bounds.Right; i++)
-				for (var j = map.Bounds.Top; j < map.Bounds.Bottom; j++)
-					explored[i, j] = true;
-
-			ExploredBounds = world.Map.Bounds;
+			explored.Clear(true);
 
 			Invalidate();
 		}
 
 		public void ResetExploration()
 		{
-			for (var i = map.Bounds.Left; i < map.Bounds.Right; i++)
-				for (var j = map.Bounds.Top; j < map.Bounds.Bottom; j++)
-					explored[i, j] = visibleCount[i, j] > 0;
+			foreach (var cell in map.Cells)
+				explored[cell] = visibleCount[cell] > 0;
 
 			Invalidate();
 		}
 
-		public bool IsExplored(CPos xy) { return IsExplored(xy.X, xy.Y); }
-		public bool IsExplored(int x, int y)
+		public bool IsExplored(CPos cell)
 		{
-			if (!map.IsInMap(x, y))
+			if (!map.Contains(cell))
 				return false;
 
 			if (Disabled || !self.World.LobbyInfo.GlobalSettings.Shroud)
 				return true;
 
-			return explored[x, y] && (generatedShroudCount[x, y] == 0 || visibleCount[x, y] > 0);
+			return explored[cell] && (generatedShroudCount[cell] == 0 || visibleCount[cell] > 0);
 		}
 
 		public bool IsExplored(Actor a)
@@ -259,16 +231,15 @@ namespace OpenRA.Traits
 			return GetVisOrigins(a).Any(o => IsExplored(o));
 		}
 
-		public bool IsVisible(CPos xy) { return IsVisible(xy.X, xy.Y); }
-		public bool IsVisible(int x, int y)
+		public bool IsVisible(CPos cell)
 		{
-			if (!map.IsInMap(x, y))
+			if (!map.Contains(cell))
 				return false;
 
 			if (Disabled || !self.World.LobbyInfo.GlobalSettings.Fog)
 				return true;
 
-			return visibleCount[x, y] > 0;
+			return visibleCount[cell] > 0;
 		}
 
 		// Actors are hidden under shroud, but not under fog by default
diff --git a/OpenRA.Game/Widgets/ViewportControllerWidget.cs b/OpenRA.Game/Widgets/ViewportControllerWidget.cs
index bdd1d213fd..bd5a5327ab 100644
--- a/OpenRA.Game/Widgets/ViewportControllerWidget.cs
+++ b/OpenRA.Game/Widgets/ViewportControllerWidget.cs
@@ -93,7 +93,7 @@ namespace OpenRA.Widgets
 		{
 			TooltipType = WorldTooltipType.None;
 			var cell = worldRenderer.Position(worldRenderer.Viewport.ViewToWorldPx(Viewport.LastMousePos)).ToCPos();
-			if (!world.Map.IsInMap(cell))
+			if (!world.Map.Contains(cell))
 				return;
 
 			if (world.ShroudObscures(cell))
diff --git a/OpenRA.Game/Widgets/WorldInteractionControllerWidget.cs b/OpenRA.Game/Widgets/WorldInteractionControllerWidget.cs
index 3b1e4e50be..4f9ab0454f 100644
--- a/OpenRA.Game/Widgets/WorldInteractionControllerWidget.cs
+++ b/OpenRA.Game/Widgets/WorldInteractionControllerWidget.cs
@@ -209,18 +209,20 @@ namespace OpenRA.Widgets
 				}
 				else if (key == Game.Settings.Keys.SelectUnitsByTypeKey)
 				{
-					var selectedTypes = World.Selection.Actors.Where(
-						x => x.Owner == World.RenderPlayer).Select(a => a.Info);
+					var selectedTypes = World.Selection.Actors
+						.Where(x => x.Owner == World.RenderPlayer)
+						.Select(a => a.Info);
+
 					Func<Actor, bool> cond = a => a.Owner == World.RenderPlayer && selectedTypes.Contains(a.Info);
-					var newSelection = SelectActorsInBox(
-						World, worldRenderer.Viewport.TopLeft, worldRenderer.Viewport.BottomRight, cond); 
+					var tl = worldRenderer.Viewport.TopLeft;
+					var br = worldRenderer.Viewport.BottomRight;
+					var newSelection = SelectActorsInBox(World, tl, br, cond);
+
 					if (newSelection.Count() > selectedTypes.Count())
 						Game.Debug("Selected across screen");
 					else
 					{
-						newSelection = World.ActorMap.ActorsInBox(
-							World.Map.Bounds.TopLeftAsCPos().TopLeft,
-							World.Map.Bounds.BottomRightAsCPos().BottomRight).Where(cond);
+						newSelection = World.ActorMap.ActorsInWorld().Where(cond);
 						Game.Debug("Selected across map");
 					}
 
diff --git a/OpenRA.Game/World.cs b/OpenRA.Game/World.cs
index 6e8d2c424d..6d1aa45475 100644
--- a/OpenRA.Game/World.cs
+++ b/OpenRA.Game/World.cs
@@ -55,17 +55,6 @@ namespace OpenRA
 		public bool ShroudObscures(Actor a) { return RenderPlayer != null && !RenderPlayer.Shroud.IsExplored(a); }
 		public bool ShroudObscures(CPos p) { return RenderPlayer != null && !RenderPlayer.Shroud.IsExplored(p); }
 
-		public Rectangle? VisibleBounds
-		{
-			get
-			{
-				if (RenderPlayer == null)
-					return null;
-
-				return RenderPlayer.Shroud.ExploredBounds;
-			}
-		}
-
 		public bool IsReplay
 		{
 			get { return orderManager.Connection is ReplayConnection; }
diff --git a/OpenRA.Mods.D2k/D2kResourceLayer.cs b/OpenRA.Mods.D2k/D2kResourceLayer.cs
index 26ea2e87c2..7438e1948a 100644
--- a/OpenRA.Mods.D2k/D2kResourceLayer.cs
+++ b/OpenRA.Mods.D2k/D2kResourceLayer.cs
@@ -97,28 +97,28 @@ namespace OpenRA.Traits
 		ClearSides FindClearSides(ResourceType t, CPos p)
 		{
 			var ret = ClearSides.None;
-			if (render[p.X, p.Y - 1].Type != t)
+			if (render[p + new CVec(0, -1)].Type != t)
 				ret |= ClearSides.Top | ClearSides.TopLeft | ClearSides.TopRight;
 
-			if (render[p.X - 1, p.Y].Type != t)
+			if (render[p + new CVec(-1, 0)].Type != t)
 				ret |= ClearSides.Left | ClearSides.TopLeft | ClearSides.BottomLeft;
 
-			if (render[p.X + 1, p.Y].Type != t)
+			if (render[p + new CVec(1, 0)].Type != t)
 				ret |= ClearSides.Right | ClearSides.TopRight | ClearSides.BottomRight;
 
-			if (render[p.X, p.Y + 1].Type != t)
+			if (render[p + new CVec(0, 1)].Type != t)
 				ret |= ClearSides.Bottom | ClearSides.BottomLeft | ClearSides.BottomRight;
 
-			if (render[p.X - 1, p.Y - 1].Type != t)
+			if (render[p + new CVec(-1, -1)].Type != t)
 				ret |= ClearSides.TopLeft;
 
-			if (render[p.X + 1, p.Y - 1].Type != t)
+			if (render[p + new CVec(1, -1)].Type != t)
 				ret |= ClearSides.TopRight;
 
-			if (render[p.X - 1, p.Y + 1].Type != t)
+			if (render[p + new CVec(-1, 1)].Type != t)
 				ret |= ClearSides.BottomLeft;
 
-			if (render[p.X + 1, p.Y + 1].Type != t)
+			if (render[p + new CVec(1, 1)].Type != t)
 				ret |= ClearSides.BottomRight;
 
 			return ret;
@@ -126,7 +126,7 @@ namespace OpenRA.Traits
 
 		void UpdateRenderedTileInner(CPos p)
 		{
-			var t = render[p.X, p.Y];
+			var t = render[p];
 			if (t.Density > 0)
 			{
 				var clear = FindClearSides(t.Type, p);
@@ -146,7 +146,7 @@ namespace OpenRA.Traits
 			else
 				t.Sprite = null;
 
-			render[p.X, p.Y] = t;
+			render[p] = t;
 		}
 
 		protected override void UpdateRenderedSprite(CPos p)
diff --git a/OpenRA.Mods.RA/Activities/MoveAdjacentTo.cs b/OpenRA.Mods.RA/Activities/MoveAdjacentTo.cs
index a2569415dc..d077a50de3 100755
--- a/OpenRA.Mods.RA/Activities/MoveAdjacentTo.cs
+++ b/OpenRA.Mods.RA/Activities/MoveAdjacentTo.cs
@@ -119,7 +119,7 @@ namespace OpenRA.Mods.RA.Activities
 
 			var path = pathFinder.FindBidiPath(
 				PathSearch.FromPoints(self.World, mobile.Info, self, searchCells, loc, true),
-				PathSearch.FromPoint(self.World, mobile.Info, self, loc, targetPosition, true).InReverse()
+				PathSearch.FromPoint(self.World, mobile.Info, self, loc, targetPosition, true).Reverse()
 			);
 
 			inner = mobile.MoveTo(() => path);
diff --git a/OpenRA.Mods.RA/Air/Aircraft.cs b/OpenRA.Mods.RA/Air/Aircraft.cs
index 5400e021c9..cd05962639 100755
--- a/OpenRA.Mods.RA/Air/Aircraft.cs
+++ b/OpenRA.Mods.RA/Air/Aircraft.cs
@@ -165,7 +165,7 @@ namespace OpenRA.Mods.RA.Air
 
 		public bool CanLand(CPos cell)
 		{
-			if (!self.World.Map.IsInMap(cell))
+			if (!self.World.Map.Contains(cell))
 				return false;
 
 			if (self.World.ActorMap.AnyUnitsAt(cell))
@@ -246,7 +246,7 @@ namespace OpenRA.Mods.RA.Air
 				return false;
 
 			IsQueued = modifiers.HasModifier(TargetModifiers.ForceQueue);
-			cursor = self.World.Map.IsInMap(target.CenterPosition.ToCPos()) ? "move" : "move-blocked";
+			cursor = self.World.Map.Contains(target.CenterPosition.ToCPos()) ? "move" : "move-blocked";
 			return true;
 		}
 
diff --git a/OpenRA.Mods.RA/Air/FlyTimed.cs b/OpenRA.Mods.RA/Air/FlyTimed.cs
index c99fdc47a6..a904281e49 100755
--- a/OpenRA.Mods.RA/Air/FlyTimed.cs
+++ b/OpenRA.Mods.RA/Air/FlyTimed.cs
@@ -34,7 +34,7 @@ namespace OpenRA.Mods.RA.Air
 	{
 		public override Activity Tick(Actor self)
 		{
-			if (IsCanceled || !self.World.Map.IsInMap(self.Location))
+			if (IsCanceled || !self.World.Map.Contains(self.Location))
 				return NextActivity;
 
 			var plane = self.Trait<Plane>();
diff --git a/OpenRA.Mods.RA/Attack/AttackBase.cs b/OpenRA.Mods.RA/Attack/AttackBase.cs
index d5ab7465b1..77fd5e0ff8 100644
--- a/OpenRA.Mods.RA/Attack/AttackBase.cs
+++ b/OpenRA.Mods.RA/Attack/AttackBase.cs
@@ -207,7 +207,7 @@ namespace OpenRA.Mods.RA
 
 			bool CanTargetLocation(Actor self, CPos location, List<Actor> actorsAtLocation, TargetModifiers modifiers, ref string cursor)
 			{
-				if (!self.World.Map.IsInMap(location))
+				if (!self.World.Map.Contains(location))
 					return false;
 
 				IsQueued = modifiers.HasModifier(TargetModifiers.ForceQueue);
diff --git a/OpenRA.Mods.RA/Bridge.cs b/OpenRA.Mods.RA/Bridge.cs
index aa34689d44..6fa095944c 100644
--- a/OpenRA.Mods.RA/Bridge.cs
+++ b/OpenRA.Mods.RA/Bridge.cs
@@ -91,14 +91,14 @@ namespace OpenRA.Mods.RA
 
 			// Set the initial custom terrain types
 			foreach (var c in footprint.Keys)
-				self.World.Map.CustomTerrain[c.X, c.Y] = GetTerrainType(c);
+				self.World.Map.CustomTerrain[c] = GetTerrainType(c);
 		}
 
 		int GetTerrainType(CPos cell)
 		{
 			var dx = cell - self.Location;
 			var index = dx.X + self.World.TileSet.Templates[template].Size.X * dx.Y;
-			return self.World.TileSet.GetTerrainIndex(new TileReference<ushort, byte>(template, (byte)index));
+			return self.World.TileSet.GetTerrainIndex(new TerrainTile(template, (byte)index));
 		}
 
 		public void LinkNeighbouringBridges(World world, BridgeLayer bridges)
@@ -121,7 +121,7 @@ namespace OpenRA.Mods.RA
 		IRenderable[] TemplateRenderables(WorldRenderer wr, PaletteReference palette, ushort template)
 		{
 			return footprint.Select(c => (IRenderable)(new SpriteRenderable(
-				wr.Theater.TileSprite(new TileReference<ushort, byte>(template, c.Value)),
+				wr.Theater.TileSprite(new TerrainTile(template, c.Value)),
 				c.Key.CenterPosition, WVec.Zero, -512, palette, 1f, true))).ToArray();
 		}
 
@@ -204,7 +204,7 @@ namespace OpenRA.Mods.RA
 
 			// Update map
 			foreach (var c in footprint.Keys)
-				self.World.Map.CustomTerrain[c.X, c.Y] = GetTerrainType(c);
+				self.World.Map.CustomTerrain[c] = GetTerrainType(c);
 
 			// If this bridge repair operation connects two pathfinding domains,
 			// update the domain index.
diff --git a/OpenRA.Mods.RA/BridgeLayer.cs b/OpenRA.Mods.RA/BridgeLayer.cs
index 365b47459c..62e3f1078e 100644
--- a/OpenRA.Mods.RA/BridgeLayer.cs
+++ b/OpenRA.Mods.RA/BridgeLayer.cs
@@ -19,95 +19,100 @@ namespace OpenRA.Mods.RA
 	class BridgeLayerInfo : ITraitInfo
 	{
 		[ActorReference]
-		public readonly string[] Bridges = {"bridge1", "bridge2"};
+		public readonly string[] Bridges = { "bridge1", "bridge2" };
 
 		public object Create(ActorInitializer init) { return new BridgeLayer(init.self, this); }
 	}
 
 	class BridgeLayer : IWorldLoaded
 	{
-		readonly BridgeLayerInfo Info;
+		readonly BridgeLayerInfo info;
 		readonly World world;
-		Dictionary<ushort, Pair<string, float>> BridgeTypes = new Dictionary<ushort, Pair<string,float>>();
-		Bridge[,] Bridges;
+		Dictionary<ushort, Pair<string, float>> bridgeTypes = new Dictionary<ushort, Pair<string, float>>();
+		CellLayer<Bridge> bridges;
 
-		public BridgeLayer(Actor self, BridgeLayerInfo Info)
+		public BridgeLayer(Actor self, BridgeLayerInfo info)
 		{
-			this.Info = Info;
+			this.info = info;
 			this.world = self.World;
 		}
 
 		public void WorldLoaded(World w, WorldRenderer wr)
 		{
-			Bridges = new Bridge[w.Map.MapSize.X, w.Map.MapSize.Y];
+			bridges = new CellLayer<Bridge>(w.Map);
 
 			// Build a list of templates that should be overlayed with bridges
-			foreach(var bridge in Info.Bridges)
+			foreach (var bridge in info.Bridges)
 			{
 				var bi = w.Map.Rules.Actors[bridge].Traits.Get<BridgeInfo>();
 				foreach (var template in bi.Templates)
-					BridgeTypes.Add(template.First, Pair.New(bridge, template.Second));
+					bridgeTypes.Add(template.First, Pair.New(bridge, template.Second));
 			}
 
 			// Loop through the map looking for templates to overlay
 			for (var i = w.Map.Bounds.Left; i < w.Map.Bounds.Right; i++)
+			{
 				for (var j = w.Map.Bounds.Top; j < w.Map.Bounds.Bottom; j++)
-					if (BridgeTypes.Keys.Contains(w.Map.MapTiles.Value[i, j].Type))
-							ConvertBridgeToActor(w, i, j);
+				{
+					var cell = new CPos(i, j);
+					if (bridgeTypes.ContainsKey(w.Map.MapTiles.Value[cell].Type))
+						ConvertBridgeToActor(w, cell);
+				}
+			}
 
 			// Link adjacent (long)-bridges so that artwork is updated correctly
 			foreach (var b in w.Actors.SelectMany(a => a.TraitsImplementing<Bridge>()))
-				b.LinkNeighbouringBridges(w,this);
+				b.LinkNeighbouringBridges(w, this);
 		}
 
-		void ConvertBridgeToActor(World w, int i, int j)
+		void ConvertBridgeToActor(World w, CPos cell)
 		{
 			// This cell already has a bridge overlaying it from a previous iteration
-			if (Bridges[i,j] != null)
+			if (bridges[cell] != null)
 				return;
 
 			// Correlate the tile "image" aka subtile with its position to find the template origin
-			var tile = w.Map.MapTiles.Value[i, j].Type;
-			var index = w.Map.MapTiles.Value[i, j].Index;
+			var tile = w.Map.MapTiles.Value[cell].Type;
+			var index = w.Map.MapTiles.Value[cell].Index;
 			var template = w.TileSet.Templates[tile];
-			var ni = i - index % template.Size.X;
-			var nj = j - index / template.Size.X;
+			var ni = cell.X - index % template.Size.X;
+			var nj = cell.Y - index / template.Size.X;
 
 			// Create a new actor for this bridge and keep track of which subtiles this bridge includes
-			var bridge = w.CreateActor(BridgeTypes[tile].First, new TypeDictionary
+			var bridge = w.CreateActor(bridgeTypes[tile].First, new TypeDictionary
 			{
 				new LocationInit(new CPos(ni, nj)),
 				new OwnerInit(w.WorldActor.Owner),
-				new HealthInit(BridgeTypes[tile].Second),
+				new HealthInit(bridgeTypes[tile].Second),
 			}).Trait<Bridge>();
 
 			var subTiles = new Dictionary<CPos, byte>();
 
 			// For each subtile in the template
-			for (byte ind = 0; ind < template.Size.X*template.Size.Y; ind++)
+			for (byte ind = 0; ind < template.Size.X * template.Size.Y; ind++)
 			{
 				// Where do we expect to find the subtile
-				var x = ni + ind % template.Size.X;
-				var y = nj + ind / template.Size.X;
+				var subtile = new CPos(ni + ind % template.Size.X, nj + ind / template.Size.X);
 
 				// This isn't the bridge you're looking for
-				if (!w.Map.IsInMap(x, y) || w.Map.MapTiles.Value[x, y].Type != tile ||
-					w.Map.MapTiles.Value[x, y].Index != ind)
+				if (!w.Map.Contains(subtile) || w.Map.MapTiles.Value[subtile].Type != tile ||
+					w.Map.MapTiles.Value[subtile].Index != ind)
 					continue;
 
-				subTiles.Add(new CPos(x, y), ind);
-				Bridges[x,y] = bridge;
+				subTiles.Add(subtile, ind);
+				bridges[subtile] = bridge;
 			}
+
 			bridge.Create(tile, subTiles);
 		}
 
 		// Used to check for neighbouring bridges
 		public Bridge GetBridge(CPos cell)
 		{
-			if (!world.Map.IsInMap(cell))
+			if (!world.Map.Contains(cell))
 				return null;
 
-			return Bridges[ cell.X, cell.Y ];
+			return bridges[cell];
 		}
 	}
 }
diff --git a/OpenRA.Mods.RA/Buildings/BuildingInfluence.cs b/OpenRA.Mods.RA/Buildings/BuildingInfluence.cs
index 6283a18ede..8ccaf15509 100755
--- a/OpenRA.Mods.RA/Buildings/BuildingInfluence.cs
+++ b/OpenRA.Mods.RA/Buildings/BuildingInfluence.cs
@@ -19,14 +19,14 @@ namespace OpenRA.Mods.RA.Buildings
 
 	public class BuildingInfluence
 	{
-		Actor[,] influence;
+		CellLayer<Actor> influence;
 		Map map;
 
 		public BuildingInfluence(World world)
 		{
 			map = world.Map;
 
-			influence = new Actor[map.MapSize.X, map.MapSize.Y];
+			influence = new CellLayer<Actor>(map);
 
 			world.ActorAdded +=	a =>
 			{
@@ -35,8 +35,8 @@ namespace OpenRA.Mods.RA.Buildings
 					return;
 
 				foreach (var u in FootprintUtils.Tiles(map.Rules, a.Info.Name, b.Info, a.Location))
-					if (map.IsInMap(u) && influence[u.X, u.Y] == null)
-						influence[u.X, u.Y] = a;
+					if (map.Contains(u) && influence[u] == null)
+						influence[u] = a;
 			};
 
 			world.ActorRemoved += a =>
@@ -46,17 +46,17 @@ namespace OpenRA.Mods.RA.Buildings
 					return;
 
 				foreach (var u in FootprintUtils.Tiles(map.Rules, a.Info.Name, b.Info, a.Location))
-					if (map.IsInMap(u) && influence[u.X, u.Y] == a)
-						influence[u.X, u.Y] = null;
+					if (map.Contains(u) && influence[u] == a)
+						influence[u] = null;
 			};
 		}
 
 		public Actor GetBuildingAt(CPos cell)
 		{
-			if (!map.IsInMap(cell))
+			if (!map.Contains(cell))
 				return null;
 
-			return influence[cell.X, cell.Y];
+			return influence[cell];
 		}
 	}
 }
diff --git a/OpenRA.Mods.RA/Buildings/LaysTerrain.cs b/OpenRA.Mods.RA/Buildings/LaysTerrain.cs
index 02e3391b4c..d375de521a 100755
--- a/OpenRA.Mods.RA/Buildings/LaysTerrain.cs
+++ b/OpenRA.Mods.RA/Buildings/LaysTerrain.cs
@@ -57,11 +57,11 @@ namespace OpenRA.Mods.RA.Buildings
 						continue;
 
 					// Don't place under other buildings or custom terrain
-					if (bi.GetBuildingAt(c) != self || map.CustomTerrain[c.X, c.Y] != -1)
+					if (bi.GetBuildingAt(c) != self || map.CustomTerrain[c] != -1)
 						continue;
 
 					var index = Game.CosmeticRandom.Next(template.TilesCount);
-					layer.AddTile(c, new TileReference<ushort, byte>(template.Id, (byte)index));
+					layer.AddTile(c, new TerrainTile(template.Id, (byte)index));
 				}
 
 				return;
@@ -77,10 +77,10 @@ namespace OpenRA.Mods.RA.Buildings
 					continue;
 
 				// Don't place under other buildings or custom terrain
-				if (bi.GetBuildingAt(c) != self || map.CustomTerrain[c.X, c.Y] != -1)
+				if (bi.GetBuildingAt(c) != self || map.CustomTerrain[c] != -1)
 					continue;
 
-				layer.AddTile(c, new TileReference<ushort, byte>(template.Id, (byte)i));
+				layer.AddTile(c, new TerrainTile(template.Id, (byte)i));
 			}
 		}
 	}
diff --git a/OpenRA.Mods.RA/Buildings/Util.cs b/OpenRA.Mods.RA/Buildings/Util.cs
index aca297f34d..89bb4d2923 100644
--- a/OpenRA.Mods.RA/Buildings/Util.cs
+++ b/OpenRA.Mods.RA/Buildings/Util.cs
@@ -26,7 +26,7 @@ namespace OpenRA.Mods.RA.Buildings
 			if (world.WorldActor.Trait<BuildingInfluence>().GetBuildingAt(a) != null) return false;
 			if (world.ActorMap.GetUnitsAt(a).Any(b => b != toIgnore)) return false;
 
-			return world.Map.IsInMap(a) && bi.TerrainTypes.Contains(world.Map.GetTerrainInfo(a).Type);
+			return world.Map.Contains(a) && bi.TerrainTypes.Contains(world.Map.GetTerrainInfo(a).Type);
 		}
 
 		public static bool CanPlaceBuilding(this World world, string name, BuildingInfo building, CPos topLeft, Actor toIgnore)
@@ -36,7 +36,7 @@ namespace OpenRA.Mods.RA.Buildings
 
 			var res = world.WorldActor.Trait<ResourceLayer>();
 			return FootprintUtils.Tiles(world.Map.Rules, name, building, topLeft).All(
-				t => world.Map.IsInMap(t.X, t.Y) && res.GetResource(t) == null &&
+				t => world.Map.Contains(t) && res.GetResource(t) == null &&
 					world.IsCellBuildable(t, building, toIgnore));
 		}
 
diff --git a/OpenRA.Mods.RA/Combat.cs b/OpenRA.Mods.RA/Combat.cs
index 85434ef1d6..ad28c5c17a 100644
--- a/OpenRA.Mods.RA/Combat.cs
+++ b/OpenRA.Mods.RA/Combat.cs
@@ -37,7 +37,7 @@ namespace OpenRA.Mods.RA
 			var world = firedBy.World;
 			var targetTile = pos.ToCPos();
 
-			if (!world.Map.IsInMap(targetTile))
+			if (!world.Map.Contains(targetTile))
 				return;
 
 			var isWater = pos.Z <= 0 && world.Map.GetTerrainInfo(targetTile).IsWater;
diff --git a/OpenRA.Mods.RA/Crate.cs b/OpenRA.Mods.RA/Crate.cs
index fa8cdd58a6..09484ef770 100644
--- a/OpenRA.Mods.RA/Crate.cs
+++ b/OpenRA.Mods.RA/Crate.cs
@@ -90,7 +90,7 @@ namespace OpenRA.Mods.RA
 
 		public bool CanEnterCell(CPos cell, Actor ignoreActor, bool checkTransientActors)
 		{
-			if (!self.World.Map.IsInMap(cell.X, cell.Y)) return false;
+			if (!self.World.Map.Contains(cell)) return false;
 
 			var type = self.World.Map.GetTerrainInfo(cell).Type;
 			if (!info.TerrainTypes.Contains(type))
diff --git a/OpenRA.Mods.RA/Effects/Missile.cs b/OpenRA.Mods.RA/Effects/Missile.cs
index 8120e0bcca..1404b41639 100755
--- a/OpenRA.Mods.RA/Effects/Missile.cs
+++ b/OpenRA.Mods.RA/Effects/Missile.cs
@@ -160,7 +160,7 @@ namespace OpenRA.Mods.RA.Effects
 				|| (dist.LengthSquared < MissileCloseEnough.Range * MissileCloseEnough.Range) // Within range
 				|| (info.RangeLimit != 0 && ticks > info.RangeLimit) // Ran out of fuel
 				|| (!info.High && world.ActorMap.GetUnitsAt(cell).Any(a => a.HasTrait<IBlocksBullets>())) // Hit a wall
-				|| !world.Map.IsInMap(cell) // This also avoids an IndexOutOfRangeException in GetTerrainInfo below.
+				|| !world.Map.Contains(cell) // This also avoids an IndexOutOfRangeException in GetTerrainInfo below.
 				|| (!string.IsNullOrEmpty(info.BoundToTerrainType) && world.Map.GetTerrainInfo(cell).Type != info.BoundToTerrainType); // Hit incompatible terrain
 
 			if (shouldExplode)
diff --git a/OpenRA.Mods.RA/Husk.cs b/OpenRA.Mods.RA/Husk.cs
index 1606c1c3f7..1fc5e813d9 100644
--- a/OpenRA.Mods.RA/Husk.cs
+++ b/OpenRA.Mods.RA/Husk.cs
@@ -54,7 +54,7 @@ namespace OpenRA.Mods.RA
 		public IEnumerable<Pair<CPos, SubCell>> OccupiedCells() { yield return Pair.New(TopLeft, SubCell.FullCell); }
 		public bool CanEnterCell(CPos cell, Actor ignoreActor, bool checkTransientActors)
 		{
-			if (!self.World.Map.IsInMap(cell.X, cell.Y))
+			if (!self.World.Map.Contains(cell))
 				return false;
 
 			if (!info.AllowedTerrain.Contains(self.World.Map.GetTerrainInfo(cell).Type))
diff --git a/OpenRA.Mods.RA/Minelayer.cs b/OpenRA.Mods.RA/Minelayer.cs
index 86bbf6f5d0..88d642bd5a 100644
--- a/OpenRA.Mods.RA/Minelayer.cs
+++ b/OpenRA.Mods.RA/Minelayer.cs
@@ -202,7 +202,7 @@ namespace OpenRA.Mods.RA
 					return false;
 
 				var location = target.CenterPosition.ToCPos();
-				if (!self.World.Map.IsInMap(location))
+				if (!self.World.Map.Contains(location))
 					return false;
 
 				cursor = "ability";
diff --git a/OpenRA.Mods.RA/Move/Mobile.cs b/OpenRA.Mods.RA/Move/Mobile.cs
index 6ede32679a..fcb964c020 100755
--- a/OpenRA.Mods.RA/Move/Mobile.cs
+++ b/OpenRA.Mods.RA/Move/Mobile.cs
@@ -101,7 +101,7 @@ namespace OpenRA.Mods.RA.Move
 
 		public int MovementCostForCell(World world, CPos cell)
 		{
-			if (!world.Map.IsInMap(cell.X, cell.Y))
+			if (!world.Map.Contains(cell))
 				return int.MaxValue;
 
 			var index = world.Map.GetTerrainIndex(cell);
@@ -580,7 +580,7 @@ namespace OpenRA.Mods.RA.Move
 				if (self.Owner.Shroud.IsExplored(location))
 					cursor = self.World.Map.GetTerrainInfo(location).CustomCursor ?? cursor;
 
-				if (!self.World.Map.IsInMap(location) || (self.Owner.Shroud.IsExplored(location) &&
+				if (!self.World.Map.Contains(location) || (self.Owner.Shroud.IsExplored(location) &&
 						unitType.MovementCostForCell(self.World, location) == int.MaxValue))
 					cursor = "move-blocked";
 
diff --git a/OpenRA.Mods.RA/Move/PathFinder.cs b/OpenRA.Mods.RA/Move/PathFinder.cs
old mode 100755
new mode 100644
index bbf4a3ad39..444fdaae57
--- a/OpenRA.Mods.RA/Move/PathFinder.cs
+++ b/OpenRA.Mods.RA/Move/PathFinder.cs
@@ -12,6 +12,7 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using OpenRA;
 using OpenRA.Primitives;
 using OpenRA.Support;
 using OpenRA.Traits;
@@ -68,7 +69,7 @@ namespace OpenRA.Mods.RA.Move
 
 				var pb = FindBidiPath(
 					PathSearch.FromPoint(world, mi, self, target, from, true),
-					PathSearch.FromPoint(world, mi, self, from, target, true).InReverse()
+					PathSearch.FromPoint(world, mi, self, from, target, true).Reverse()
 				);
 
 				CheckSanePath2(pb, from, target);
@@ -109,7 +110,7 @@ namespace OpenRA.Mods.RA.Move
 
 				var path = FindBidiPath(
 					PathSearch.FromPoints(world, mi, self, tilesInRange, src, true),
-					PathSearch.FromPoint(world, mi, self, src, targetCell, true).InReverse()
+					PathSearch.FromPoint(world, mi, self, src, targetCell, true).Reverse()
 				);
 
 				return path;
@@ -124,21 +125,19 @@ namespace OpenRA.Mods.RA.Move
 				{
 					List<CPos> path = null;
 
-					while (!search.queue.Empty)
+					while (!search.Queue.Empty)
 					{
 						var p = search.Expand(world);
-						if (search.heuristic(p) == 0)
+						if (search.Heuristic(p) == 0)
 						{
-							path = MakePath(search.cellInfo, p);
+							path = MakePath(search.CellInfo, p);
 							break;
 						}
 					}
 
 					var dbg = world.WorldActor.TraitOrDefault<PathfinderDebugOverlay>();
 					if (dbg != null)
-					{
-						dbg.AddLayer(search.considered.Select(p => new Pair<CPos, int>(p, search.cellInfo[p.X, p.Y].MinCost)), search.maxCost, search.owner);
-					}
+						dbg.AddLayer(search.Considered.Select(p => new Pair<CPos, int>(p, search.CellInfo[p].MinCost)), search.MaxCost, search.Owner);
 
 					if (path != null)
 						return path;
@@ -149,15 +148,15 @@ namespace OpenRA.Mods.RA.Move
 			}
 		}
 
-		static List<CPos> MakePath(CellInfo[,] cellInfo, CPos destination)
+		static List<CPos> MakePath(CellLayer<CellInfo> cellInfo, CPos destination)
 		{
 			var ret = new List<CPos>();
 			var pathNode = destination;
 
-			while (cellInfo[pathNode.X, pathNode.Y].Path != pathNode)
+			while (cellInfo[pathNode].Path != pathNode)
 			{
 				ret.Add(pathNode);
-				pathNode = cellInfo[pathNode.X, pathNode.Y].Path;
+				pathNode = cellInfo[pathNode].Path;
 			}
 
 			ret.Add(pathNode);
@@ -165,9 +164,8 @@ namespace OpenRA.Mods.RA.Move
 			return ret;
 		}
 
-		public List<CPos> FindBidiPath(			/* searches from both ends toward each other */
-			PathSearch fromSrc,
-			PathSearch fromDest)
+		// Searches from both ends toward each other
+		public List<CPos> FindBidiPath(PathSearch fromSrc, PathSearch fromDest)
 		{
 			using (new PerfSample("Pathfinder"))
 			{
@@ -176,13 +174,13 @@ namespace OpenRA.Mods.RA.Move
 				{
 					List<CPos> path = null;
 
-					while (!fromSrc.queue.Empty && !fromDest.queue.Empty)
+					while (!fromSrc.Queue.Empty && !fromDest.Queue.Empty)
 					{
 						/* make some progress on the first search */
 						var p = fromSrc.Expand(world);
 
-						if (fromDest.cellInfo[p.X, p.Y].Seen &&
-							fromDest.cellInfo[p.X, p.Y].MinCost < float.PositiveInfinity)
+						if (fromDest.CellInfo[p].Seen &&
+							fromDest.CellInfo[p].MinCost < float.PositiveInfinity)
 						{
 							path = MakeBidiPath(fromSrc, fromDest, p);
 							break;
@@ -191,8 +189,8 @@ namespace OpenRA.Mods.RA.Move
 						/* make some progress on the second search */
 						var q = fromDest.Expand(world);
 
-						if (fromSrc.cellInfo[q.X, q.Y].Seen &&
-							fromSrc.cellInfo[q.X, q.Y].MinCost < float.PositiveInfinity)
+						if (fromSrc.CellInfo[q].Seen &&
+							fromSrc.CellInfo[q].MinCost < float.PositiveInfinity)
 						{
 							path = MakeBidiPath(fromSrc, fromDest, q);
 							break;
@@ -202,8 +200,8 @@ namespace OpenRA.Mods.RA.Move
 					var dbg = world.WorldActor.TraitOrDefault<PathfinderDebugOverlay>();
 					if (dbg != null)
 					{
-						dbg.AddLayer(fromSrc.considered.Select(p => new Pair<CPos, int>(p, fromSrc.cellInfo[p.X, p.Y].MinCost)), fromSrc.maxCost, fromSrc.owner);
-						dbg.AddLayer(fromDest.considered.Select(p => new Pair<CPos, int>(p, fromDest.cellInfo[p.X, p.Y].MinCost)), fromDest.maxCost, fromDest.owner);
+						dbg.AddLayer(fromSrc.Considered.Select(p => new Pair<CPos, int>(p, fromSrc.CellInfo[p].MinCost)), fromSrc.MaxCost, fromSrc.Owner);
+						dbg.AddLayer(fromDest.Considered.Select(p => new Pair<CPos, int>(p, fromDest.CellInfo[p].MinCost)), fromDest.MaxCost, fromDest.Owner);
 					}
 
 					if (path != null)
@@ -216,25 +214,25 @@ namespace OpenRA.Mods.RA.Move
 
 		static List<CPos> MakeBidiPath(PathSearch a, PathSearch b, CPos p)
 		{
-			var ca = a.cellInfo;
-			var cb = b.cellInfo;
+			var ca = a.CellInfo;
+			var cb = b.CellInfo;
 
 			var ret = new List<CPos>();
 
 			var q = p;
-			while (ca[q.X, q.Y].Path != q)
+			while (ca[q].Path != q)
 			{
 				ret.Add(q);
-				q = ca[q.X, q.Y].Path;
+				q = ca[q].Path;
 			}
 			ret.Add(q);
 
 			ret.Reverse();
 
 			q = p;
-			while (cb[q.X, q.Y].Path != q)
+			while (cb[q].Path != q)
 			{
-				q = cb[q.X, q.Y].Path;
+				q = cb[q].Path;
 				ret.Add(q);
 			}
 
@@ -286,8 +284,8 @@ namespace OpenRA.Mods.RA.Move
 
 	public struct PathDistance : IComparable<PathDistance>
 	{
-		public int EstTotal;
-		public CPos Location;
+		public readonly int EstTotal;
+		public readonly CPos Location;
 
 		public PathDistance(int estTotal, CPos location)
 		{
diff --git a/OpenRA.Mods.RA/Move/PathSearch.cs b/OpenRA.Mods.RA/Move/PathSearch.cs
index b453a00a26..1b61a86814 100755
--- a/OpenRA.Mods.RA/Move/PathSearch.cs
+++ b/OpenRA.Mods.RA/Move/PathSearch.cs
@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2011 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
  * This file is part of OpenRA, which is free software. It is made
  * available to you under the terms of the GNU General Public License
  * as published by the Free Software Foundation. For more information,
@@ -10,45 +10,97 @@
 
 using System;
 using System.Collections.Generic;
+using System.Drawing;
 using System.Linq;
+using OpenRA;
 using OpenRA.Primitives;
 
 namespace OpenRA.Mods.RA.Move
 {
 	public sealed class PathSearch : IDisposable
 	{
-		World world;
-		public CellInfo[,] cellInfo;
-		public PriorityQueue<PathDistance> queue;
-		public Func<CPos, int> heuristic;
+		public CellLayer<CellInfo> CellInfo;
+		public PriorityQueue<PathDistance> Queue;
+		public Func<CPos, int> Heuristic;
+		public bool CheckForBlocked;
+		public Actor IgnoreBuilding;
+		public bool InReverse;
+		public HashSet<CPos> Considered;
+		public Player Owner { get { return self.Owner; } }
+		public int MaxCost;
+
+		Actor self;
+		MobileInfo mobileInfo;
 		Func<CPos, int> customCost;
 		Func<CPos, bool> customBlock;
-		public bool checkForBlocked;
-		public Actor ignoreBuilding;
-		public bool inReverse;
-		public HashSet<CPos> considered;
-		public int maxCost;
 		Pair<CVec, int>[] nextDirections;
-		MobileInfo mobileInfo;
-		Actor self;
-		public Player owner { get { return self.Owner; } }
+		int laneBias = 1;
 
 		public PathSearch(World world, MobileInfo mobileInfo, Actor self)
 		{
-			this.world = world;
-			cellInfo = InitCellInfo();
+			this.self = self;
+			CellInfo = InitCellInfo();
 			this.mobileInfo = mobileInfo;
 			this.self = self;
 			customCost = null;
-			queue = new PriorityQueue<PathDistance>();
-			considered = new HashSet<CPos>();
-			maxCost = 0;
+			Queue = new PriorityQueue<PathDistance>();
+			Considered = new HashSet<CPos>();
+			MaxCost = 0;
 			nextDirections = CVec.directions.Select(d => new Pair<CVec, int>(d, 0)).ToArray();
 		}
 
-		public PathSearch InReverse()
+		public static PathSearch Search(World world, MobileInfo mi, Actor self, bool checkForBlocked)
 		{
-			inReverse = true;
+			var search = new PathSearch(world, mi, self)
+			{
+				CheckForBlocked = checkForBlocked
+			};
+
+			return search;
+		}
+
+		public static PathSearch FromPoint(World world, MobileInfo mi, Actor self, CPos from, CPos target, bool checkForBlocked)
+		{
+			var search = new PathSearch(world, mi, self)
+			{
+				Heuristic = DefaultEstimator(target),
+				CheckForBlocked = checkForBlocked
+			};
+
+			search.AddInitialCell(from);
+			return search;
+		}
+
+		public static PathSearch FromPoints(World world, MobileInfo mi, Actor self, IEnumerable<CPos> froms, CPos target, bool checkForBlocked)
+		{
+			var search = new PathSearch(world, mi, self)
+			{
+				Heuristic = DefaultEstimator(target),
+				CheckForBlocked = checkForBlocked
+			};
+
+			foreach (var sl in froms)
+				search.AddInitialCell(sl);
+
+			return search;
+		}
+
+		public static Func<CPos, int> DefaultEstimator(CPos destination)
+		{
+			return here =>
+			{
+				var diag = Math.Min(Math.Abs(here.X - destination.X), Math.Abs(here.Y - destination.Y));
+				var straight = Math.Abs(here.X - destination.X) + Math.Abs(here.Y - destination.Y);
+
+				// HACK: this relies on fp and cell-size assumptions.
+				var h = (3400 * diag / 24) + 100 * (straight - (2 * diag));
+				return (int)(h * 1.001);
+			};
+		}
+
+		public PathSearch Reverse()
+		{
+			InReverse = true;
 			return this;
 		}
 
@@ -60,13 +112,13 @@ namespace OpenRA.Mods.RA.Move
 
 		public PathSearch WithIgnoredBuilding(Actor b)
 		{
-			ignoreBuilding = b;
+			IgnoreBuilding = b;
 			return this;
 		}
 
 		public PathSearch WithHeuristic(Func<CPos, int> h)
 		{
-			heuristic = h;
+			Heuristic = h;
 			return this;
 		}
 
@@ -78,7 +130,7 @@ namespace OpenRA.Mods.RA.Move
 
 		public PathSearch WithoutLaneBias()
 		{
-			LaneBias = 0;
+			laneBias = 0;
 			return this;
 		}
 
@@ -88,18 +140,20 @@ namespace OpenRA.Mods.RA.Move
 			return this;
 		}
 
-		int LaneBias = 1;
-
 		public CPos Expand(World world)
 		{
-			var p = queue.Pop();
-			while (cellInfo[p.Location.X, p.Location.Y].Seen)
-				if (queue.Empty)
+			var p = Queue.Pop();
+			while (CellInfo[p.Location].Seen)
+			{
+				if (Queue.Empty)
 					return p.Location;
-				else
-					p = queue.Pop();
 
-			cellInfo[p.Location.X, p.Location.Y].Seen = true;
+				p = Queue.Pop();
+			}
+
+			var pCell = CellInfo[p.Location];
+			pCell.Seen = true;
+			CellInfo[p.Location] = pCell;
 
 			var thisCost = mobileInfo.MovementCostForCell(world, p.Location);
 
@@ -114,7 +168,7 @@ namespace OpenRA.Mods.RA.Move
 			}
 
 			// This current cell is ok; check all immediate directions:
-			considered.Add(p.Location);
+			Considered.Add(p.Location);
 
 			for (var i = 0; i < nextDirections.Length; ++i)
 			{
@@ -124,9 +178,10 @@ namespace OpenRA.Mods.RA.Move
 				var newHere = p.Location + d;
 
 				// Is this direction flat-out unusable or already seen?
-				if (!world.Map.IsInMap(newHere.X, newHere.Y))
+				if (!world.Map.Contains(newHere))
 					continue;
-				if (cellInfo[newHere.X, newHere.Y].Seen)
+
+				if (CellInfo[newHere].Seen)
 					continue;
 
 				// Now we may seriously consider this direction using heuristics:
@@ -135,18 +190,19 @@ namespace OpenRA.Mods.RA.Move
 				if (costHere == int.MaxValue)
 					continue;
 
-				if (!mobileInfo.CanEnterCell(world, self, newHere, ignoreBuilding, checkForBlocked, false))
+				if (!mobileInfo.CanEnterCell(world, self, newHere, IgnoreBuilding, CheckForBlocked, false))
 					continue;
 
 				if (customBlock != null && customBlock(newHere))
 					continue;
 
-				var est = heuristic(newHere);
+				var est = Heuristic(newHere);
 				if (est == int.MaxValue)
 					continue;
 
 				var cellCost = costHere;
-				if (d.X * d.Y != 0) cellCost = (cellCost * 34) / 24;
+				if (d.X * d.Y != 0)
+					cellCost = (cellCost * 34) / 24;
 
 				var userCost = 0;
 				if (customCost != null)
@@ -156,105 +212,82 @@ namespace OpenRA.Mods.RA.Move
 				}
 
 				// directional bonuses for smoother flow!
-				if (LaneBias != 0)
+				if (laneBias != 0)
 				{
-					var ux = (newHere.X + (inReverse ? 1 : 0) & 1);
-					var uy = (newHere.Y + (inReverse ? 1 : 0) & 1);
+					var ux = newHere.X + (InReverse ? 1 : 0) & 1;
+					var uy = newHere.Y + (InReverse ? 1 : 0) & 1;
 
-					if (ux == 0 && d.Y < 0) cellCost += LaneBias;
-					else if (ux == 1 && d.Y > 0) cellCost += LaneBias;
-					if (uy == 0 && d.X < 0) cellCost += LaneBias;
-					else if (uy == 1 && d.X > 0) cellCost += LaneBias;
+					if (ux == 0 && d.Y < 0)
+						cellCost += laneBias;
+					else if (ux == 1 && d.Y > 0)
+						cellCost += laneBias;
+
+					if (uy == 0 && d.X < 0)
+						cellCost += laneBias;
+					else if (uy == 1 && d.X > 0)
+						cellCost += laneBias;
 				}
 
-				var newCost = cellInfo[p.Location.X, p.Location.Y].MinCost + cellCost;
+				var newCost = CellInfo[p.Location].MinCost + cellCost;
 
 				// Cost is even higher; next direction:
-				if (newCost > cellInfo[newHere.X, newHere.Y].MinCost)
+				if (newCost > CellInfo[newHere].MinCost)
 					continue;
 
-				cellInfo[newHere.X, newHere.Y].Path = p.Location;
-				cellInfo[newHere.X, newHere.Y].MinCost = newCost;
+				var hereCell = CellInfo[newHere];
+				hereCell.Path = p.Location;
+				hereCell.MinCost = newCost;
+				CellInfo[newHere] = hereCell;
 
 				nextDirections[i].Second = newCost + est;
-				queue.Add(new PathDistance(newCost + est, newHere));
+				Queue.Add(new PathDistance(newCost + est, newHere));
 
-				if (newCost > maxCost) maxCost = newCost;
-				considered.Add(newHere);
+				if (newCost > MaxCost)
+					MaxCost = newCost;
+
+				Considered.Add(newHere);
 			}
 
 			// Sort to prefer the cheaper direction:
-			//Array.Sort(nextDirections, (a, b) => a.Second.CompareTo(b.Second));
-
+			// Array.Sort(nextDirections, (a, b) => a.Second.CompareTo(b.Second));
 			return p.Location;
 		}
 
 		public void AddInitialCell(CPos location)
 		{
-			if (!world.Map.IsInMap(location.X, location.Y))
+			if (!self.World.Map.Contains(location))
 				return;
 
-			cellInfo[location.X, location.Y] = new CellInfo(0, location, false);
-			queue.Add(new PathDistance(heuristic(location), location));
+			CellInfo[location] = new CellInfo(0, location, false);
+			Queue.Add(new PathDistance(Heuristic(location), location));
 		}
 
-		public static PathSearch Search(World world, MobileInfo mi, Actor self, bool checkForBlocked)
+		static readonly Queue<CellLayer<CellInfo>> CellInfoPool = new Queue<CellLayer<CellInfo>>();
+
+		static CellLayer<CellInfo> GetFromPool()
 		{
-			var search = new PathSearch(world, mi, self)
-			{
-				checkForBlocked = checkForBlocked
-			};
-			return search;
+			lock (CellInfoPool)
+				return CellInfoPool.Dequeue();
 		}
 
-		public static PathSearch FromPoint(World world, MobileInfo mi, Actor self, CPos from, CPos target, bool checkForBlocked)
+		static void PutBackIntoPool(CellLayer<CellInfo> ci)
 		{
-			var search = new PathSearch(world, mi, self)
-			{
-				heuristic = DefaultEstimator(target),
-				checkForBlocked = checkForBlocked
-			};
-
-			search.AddInitialCell(from);
-			return search;
+			lock (CellInfoPool)
+				CellInfoPool.Enqueue(ci);
 		}
 
-		public static PathSearch FromPoints(World world, MobileInfo mi, Actor self, IEnumerable<CPos> froms, CPos target, bool checkForBlocked)
+		CellLayer<CellInfo> InitCellInfo()
 		{
-			var search = new PathSearch(world, mi, self)
-			{
-				heuristic = DefaultEstimator(target),
-				checkForBlocked = checkForBlocked
-			};
+			CellLayer<CellInfo> result = null;
+			var mapSize = new Size(self.World.Map.MapSize.X, self.World.Map.MapSize.Y);
 
-			foreach (var sl in froms)
-				search.AddInitialCell(sl);
-
-			return search;
-		}
-
-		static readonly Queue<CellInfo[,]> cellInfoPool = new Queue<CellInfo[,]>();
-
-		static CellInfo[,] GetFromPool()
-		{
-			lock (cellInfoPool)
-				return cellInfoPool.Dequeue();
-		}
-
-		static void PutBackIntoPool(CellInfo[,] ci)
-		{
-			lock (cellInfoPool)
-				cellInfoPool.Enqueue(ci);
-		}
-
-		CellInfo[,] InitCellInfo()
-		{
-			CellInfo[,] result = null;
-			while (cellInfoPool.Count > 0)
+			// HACK: Uses a static cache so that double-ended searches (which have two PathSearch instances)
+			// can implicitly share data.  The PathFinder should allocate the CellInfo array and pass it
+			// explicitly to the things that need to share it.
+			while (CellInfoPool.Count > 0)
 			{
 				var cellInfo = GetFromPool();
-				if (cellInfo.GetUpperBound(0) != world.Map.MapSize.X - 1 ||
-					cellInfo.GetUpperBound(1) != world.Map.MapSize.Y - 1)
+				if (cellInfo.Size != mapSize)
 				{
 					Log.Write("debug", "Discarding old pooled CellInfo of wrong size.");
 					continue;
@@ -265,36 +298,24 @@ namespace OpenRA.Mods.RA.Move
 			}
 
 			if (result == null)
-				result = new CellInfo[world.Map.MapSize.X, world.Map.MapSize.Y];
+				result = new CellLayer<CellInfo>(self.World.Map);
 
-			for (var x = 0; x < world.Map.MapSize.X; x++)
-				for (var y = 0; y < world.Map.MapSize.Y; y++)
-					result[ x, y ] = new CellInfo( int.MaxValue, new CPos( x, y ), false );
+			foreach (var cell in self.World.Map.Cells)
+				result[cell] = new CellInfo(int.MaxValue, cell, false);
 
 			return result;
 		}
 
-		public static Func<CPos, int> DefaultEstimator(CPos destination)
-		{
-			return here =>
-			{
-				var diag = Math.Min(Math.Abs(here.X - destination.X), Math.Abs(here.Y - destination.Y));
-				var straight = (Math.Abs(here.X - destination.X) + Math.Abs(here.Y - destination.Y));
-				var h = (3400 * diag / 24) + 100 * (straight - (2 * diag));
-				h = (int)(h * 1.001);
-				return h;
-			};
-		}
-
 		bool disposed;
 		public void Dispose()
 		{
 			if (disposed)
 				return;
+
 			disposed = true;
 
-			PutBackIntoPool(cellInfo);
-			cellInfo = null;
+			PutBackIntoPool(CellInfo);
+			CellInfo = null;
 
 			GC.SuppressFinalize(this);
 		}
diff --git a/OpenRA.Mods.RA/RallyPoint.cs b/OpenRA.Mods.RA/RallyPoint.cs
index 2fcb3f660d..3257659ab6 100755
--- a/OpenRA.Mods.RA/RallyPoint.cs
+++ b/OpenRA.Mods.RA/RallyPoint.cs
@@ -63,7 +63,7 @@ namespace OpenRA.Mods.RA
 					return false;
 
 				var location = target.CenterPosition.ToCPos();
-				if (self.World.Map.IsInMap(location))
+				if (self.World.Map.Contains(location))
 				{
 					cursor = "ability";
 					return true;
diff --git a/OpenRA.Mods.RA/Render/RenderLandingCraft.cs b/OpenRA.Mods.RA/Render/RenderLandingCraft.cs
index 4203ed44b1..100c5a4a3f 100644
--- a/OpenRA.Mods.RA/Render/RenderLandingCraft.cs
+++ b/OpenRA.Mods.RA/Render/RenderLandingCraft.cs
@@ -44,7 +44,7 @@ namespace OpenRA.Mods.RA.Render
 			if (self.CenterPosition.Z > 0 || move.IsMoving)
 				return false;
 
-			return cargo.CurrentAdjacentCells.Any(c => self.World.Map.IsInMap(c)
+			return cargo.CurrentAdjacentCells.Any(c => self.World.Map.Contains(c)
 				&& info.OpenTerrainTypes.Contains(self.World.Map.GetTerrainInfo(c).Type));
 		}
 
diff --git a/OpenRA.Mods.RA/ShroudRenderer.cs b/OpenRA.Mods.RA/ShroudRenderer.cs
index d7ac87c25f..433a229b7e 100644
--- a/OpenRA.Mods.RA/ShroudRenderer.cs
+++ b/OpenRA.Mods.RA/ShroudRenderer.cs
@@ -10,6 +10,7 @@
 
 using System.Drawing;
 using System.Linq;
+using OpenRA;
 using OpenRA.Graphics;
 using OpenRA.Traits;
 
@@ -35,36 +36,41 @@ namespace OpenRA.Mods.RA
 
 	public class ShroudRenderer : IRenderShroud, IWorldLoaded
 	{
-		struct ShroudTile
+		class ShroudTile
 		{
-			public CPos Position;
-			public float2 ScreenPosition;
-			public int Variant;
+			public readonly CPos Position;
+			public readonly float2 ScreenPosition;
+			public readonly int Variant;
 
 			public Sprite Fog;
 			public Sprite Shroud;
+
+			public ShroudTile(CPos position, float2 screenPosition, int variant)
+			{
+				Position = position;
+				ScreenPosition = screenPosition;
+				Variant = variant;
+			}
 		}
 
+		ShroudRendererInfo info;
 		Sprite[] sprites;
 		Sprite unexploredTile;
 		int[] spriteMap;
 
-		ShroudTile[] tiles;
-		int tileStride, variantStride;
+		CellLayer<ShroudTile> tiles;
+		int variantStride;
 
 		int shroudHash;
 		PaletteReference fogPalette, shroudPalette;
-		Rectangle bounds;
-		bool useExtendedIndex;
+		Map map;
 
 		public ShroudRenderer(World world, ShroudRendererInfo info)
 		{
-			var map = world.Map;
-			bounds = map.Bounds;
-			useExtendedIndex = info.UseExtendedIndex;
+			this.info = info;
+			map = world.Map;
 
-			tiles = new ShroudTile[map.MapSize.X * map.MapSize.Y];
-			tileStride = map.MapSize.X;
+			tiles = new CellLayer<ShroudTile>(map);
 
 			// Force update on first render
 			shroudHash = -1;
@@ -80,14 +86,10 @@ namespace OpenRA.Mods.RA
 			}
 
 			// Mapping of shrouded directions -> sprite index
-			spriteMap = new int[useExtendedIndex ? 256 : 16];
+			spriteMap = new int[info.UseExtendedIndex ? 256 : 16];
 			for (var i = 0; i < info.Index.Length; i++)
 				spriteMap[info.Index[i]] = i;
 
-			// Set individual tile variants to reduce tiling
-			for (var i = 0; i < tiles.Length; i++)
-				tiles[i].Variant = Game.CosmeticRandom.Next(info.Variants.Length);
-
 			// Synthesize unexplored tile if it isn't defined
 			if (!info.Index.Contains(0))
 			{
@@ -102,21 +104,21 @@ namespace OpenRA.Mods.RA
 
 		static int FoggedEdges(Shroud s, CPos p, bool useExtendedIndex)
 		{
-			if (!s.IsVisible(p.X, p.Y))
+			if (!s.IsVisible(p))
 				return 15;
 
 			// If a side is shrouded then we also count the corners
 			var u = 0;
-			if (!s.IsVisible(p.X, p.Y - 1)) u |= 0x13;
-			if (!s.IsVisible(p.X + 1, p.Y)) u |= 0x26;
-			if (!s.IsVisible(p.X, p.Y + 1)) u |= 0x4C;
-			if (!s.IsVisible(p.X - 1, p.Y)) u |= 0x89;
+			if (!s.IsVisible(p + new CVec(0, -1))) u |= 0x13;
+			if (!s.IsVisible(p + new CVec(1, 0))) u |= 0x26;
+			if (!s.IsVisible(p + new CVec(0, 1))) u |= 0x4C;
+			if (!s.IsVisible(p + new CVec(-1, 0))) u |= 0x89;
 
 			var uside = u & 0x0F;
-			if (!s.IsVisible(p.X - 1, p.Y - 1)) u |= 0x01;
-			if (!s.IsVisible(p.X + 1, p.Y - 1)) u |= 0x02;
-			if (!s.IsVisible(p.X + 1, p.Y + 1)) u |= 0x04;
-			if (!s.IsVisible(p.X - 1, p.Y + 1)) u |= 0x08;
+			if (!s.IsVisible(p + new CVec(-1, -1))) u |= 0x01;
+			if (!s.IsVisible(p + new CVec(1, -1))) u |= 0x02;
+			if (!s.IsVisible(p + new CVec(1, 1))) u |= 0x04;
+			if (!s.IsVisible(p + new CVec(-1, 1))) u |= 0x08;
 
 			// RA provides a set of frames for tiles with shrouded
 			// corners but unshrouded edges. We want to detect this
@@ -129,21 +131,21 @@ namespace OpenRA.Mods.RA
 
 		static int ShroudedEdges(Shroud s, CPos p, bool useExtendedIndex)
 		{
-			if (!s.IsExplored(p.X, p.Y))
+			if (!s.IsExplored(p))
 				return 15;
 
 			// If a side is shrouded then we also count the corners
 			var u = 0;
-			if (!s.IsExplored(p.X, p.Y - 1)) u |= 0x13;
-			if (!s.IsExplored(p.X + 1, p.Y)) u |= 0x26;
-			if (!s.IsExplored(p.X, p.Y + 1)) u |= 0x4C;
-			if (!s.IsExplored(p.X - 1, p.Y)) u |= 0x89;
+			if (!s.IsExplored(p + new CVec(0, -1))) u |= 0x13;
+			if (!s.IsExplored(p + new CVec(1, 0))) u |= 0x26;
+			if (!s.IsExplored(p + new CVec(0, 1))) u |= 0x4C;
+			if (!s.IsExplored(p + new CVec(-1, 0))) u |= 0x89;
 
 			var uside = u & 0x0F;
-			if (!s.IsExplored(p.X - 1, p.Y - 1)) u |= 0x01;
-			if (!s.IsExplored(p.X + 1, p.Y - 1)) u |= 0x02;
-			if (!s.IsExplored(p.X + 1, p.Y + 1)) u |= 0x04;
-			if (!s.IsExplored(p.X - 1, p.Y + 1)) u |= 0x08;
+			if (!s.IsExplored(p + new CVec(-1, -1))) u |= 0x01;
+			if (!s.IsExplored(p + new CVec(1, -1))) u |= 0x02;
+			if (!s.IsExplored(p + new CVec(1, 1))) u |= 0x04;
+			if (!s.IsExplored(p + new CVec(-1, 1))) u |= 0x08;
 
 			// RA provides a set of frames for tiles with shrouded
 			// corners but unshrouded edges. We want to detect this
@@ -173,15 +175,12 @@ namespace OpenRA.Mods.RA
 
 		public void WorldLoaded(World w, WorldRenderer wr)
 		{
-			// Cache the tile positions to avoid unnecessary calculations
-			for (var i = bounds.Left; i < bounds.Right; i++)
+			// Initialize tile cache
+			foreach (var cell in map.Cells)
 			{
-				for (var j = bounds.Top; j < bounds.Bottom; j++)
-				{
-					var k = j * tileStride + i;
-					tiles[k].Position = new CPos(i, j);
-					tiles[k].ScreenPosition = wr.ScreenPosition(tiles[k].Position.CenterPosition);
-				}
+				var screen = wr.ScreenPosition(cell.CenterPosition);
+				var variant = Game.CosmeticRandom.Next(info.Variants.Length);
+				tiles[cell] = new ShroudTile(cell, screen, variant);
 			}
 
 			fogPalette = wr.Palette("fog");
@@ -209,22 +208,25 @@ namespace OpenRA.Mods.RA
 			if (shroud == null)
 			{
 				// Players with no shroud see the whole map so we only need to set the edges
-				for (var k = 0; k < tiles.Length; k++)
+				foreach (var cell in map.Cells)
 				{
-					var shrouded = ObserverShroudedEdges(tiles[k].Position, bounds, useExtendedIndex);
-					tiles[k].Shroud = GetTile(shrouded, tiles[k].Variant);
-					tiles[k].Fog = GetTile(shrouded, tiles[k].Variant);
+					var t = tiles[cell];
+					var shrouded = ObserverShroudedEdges(t.Position, map.Bounds, info.UseExtendedIndex);
+
+					t.Shroud = GetTile(shrouded, t.Variant);
+					t.Fog = GetTile(shrouded, t.Variant);
 				}
 			}
 			else
 			{
-				for (var k = 0; k < tiles.Length; k++)
+				foreach (var cell in map.Cells)
 				{
-					var shrouded = ShroudedEdges(shroud, tiles[k].Position, useExtendedIndex);
-					var fogged = FoggedEdges(shroud, tiles[k].Position, useExtendedIndex);
+					var t = tiles[cell];
+					var shrouded = ShroudedEdges(shroud, t.Position, info.UseExtendedIndex);
+					var fogged = FoggedEdges(shroud, t.Position, info.UseExtendedIndex);
 
-					tiles[k].Shroud = GetTile(shrouded, tiles[k].Variant);
-					tiles[k].Fog = GetTile(fogged, tiles[k].Variant);
+					t.Shroud = GetTile(shrouded, t.Variant);
+					t.Fog = GetTile(fogged, t.Variant);
 				}
 			}
 		}
@@ -233,27 +235,20 @@ namespace OpenRA.Mods.RA
 		{
 			Update(shroud);
 
-			var clip = wr.Viewport.CellBounds;
-			var width = clip.Width;
-			for (var j = clip.Top; j < clip.Bottom; j++)
+			foreach (var cell in wr.Viewport.VisibleCells)
 			{
-				var start = j * tileStride + clip.Left;
-				for (var k = 0; k < width; k++)
+				var t = tiles[cell];
+
+				if (t.Shroud != null)
 				{
-					var s = tiles[start + k].Shroud;
-					var f = tiles[start + k].Fog;
+					var pos = t.ScreenPosition - 0.5f * t.Shroud.size;
+					Game.Renderer.WorldSpriteRenderer.DrawSprite(t.Shroud, pos, shroudPalette);
+				}
 
-					if (s != null)
-					{
-						var pos = tiles[start + k].ScreenPosition - 0.5f * s.size;
-						Game.Renderer.WorldSpriteRenderer.DrawSprite(s, pos, shroudPalette);
-					}
-
-					if (f != null)
-					{
-						var pos = tiles[start + k].ScreenPosition - 0.5f * f.size;
-						Game.Renderer.WorldSpriteRenderer.DrawSprite(f, pos, fogPalette);
-					}
+				if (t.Fog != null)
+				{
+					var pos = t.ScreenPosition - 0.5f * t.Fog.size;
+					Game.Renderer.WorldSpriteRenderer.DrawSprite(t.Fog, pos, fogPalette);
 				}
 			}
 		}
diff --git a/OpenRA.Mods.RA/SupportPowers/SupportPowerManager.cs b/OpenRA.Mods.RA/SupportPowers/SupportPowerManager.cs
index 2220f07b5a..ec7fb92a10 100644
--- a/OpenRA.Mods.RA/SupportPowers/SupportPowerManager.cs
+++ b/OpenRA.Mods.RA/SupportPowers/SupportPowerManager.cs
@@ -245,7 +245,7 @@ namespace OpenRA.Mods.RA
 		public IEnumerable<Order> Order(World world, CPos xy, MouseInput mi)
 		{
 			world.CancelInputMode();
-			if (mi.Button == expectedButton && world.Map.IsInMap(xy))
+			if (mi.Button == expectedButton && world.Map.Contains(xy))
 				yield return new Order(order, manager.self, false) { TargetLocation = xy, SuppressVisualFeedback = true };
 		}
 
@@ -258,6 +258,6 @@ namespace OpenRA.Mods.RA
 
 		public IEnumerable<IRenderable> Render(WorldRenderer wr, World world) { yield break; }
 		public void RenderAfterWorld(WorldRenderer wr, World world) { }
-		public string GetCursor(World world, CPos xy, MouseInput mi) { return world.Map.IsInMap(xy) ? cursor : "generic-blocked"; }
+		public string GetCursor(World world, CPos xy, MouseInput mi) { return world.Map.Contains(xy) ? cursor : "generic-blocked"; }
 	}
 }
diff --git a/OpenRA.Mods.RA/World/BuildableTerrainLayer.cs b/OpenRA.Mods.RA/World/BuildableTerrainLayer.cs
index 4a07267f9f..e580673c99 100644
--- a/OpenRA.Mods.RA/World/BuildableTerrainLayer.cs
+++ b/OpenRA.Mods.RA/World/BuildableTerrainLayer.cs
@@ -32,9 +32,9 @@ namespace OpenRA.Mods.RA
 			dirty = new Dictionary<CPos, Sprite>();
 		}
 
-		public void AddTile(CPos cell, TileReference<ushort, byte> tile)
+		public void AddTile(CPos cell, TerrainTile tile)
 		{
-			map.CustomTerrain[cell.X, cell.Y] = tileset.GetTerrainIndex(tile);
+			map.CustomTerrain[cell] = tileset.GetTerrainIndex(tile);
 
 			// Terrain tiles define their origin at the topleft
 			var s = theater.TileSprite(tile);
@@ -59,12 +59,11 @@ namespace OpenRA.Mods.RA
 
 		public void Render(WorldRenderer wr)
 		{
-			var cliprect = wr.Viewport.CellBounds;
 			var pal = wr.Palette("terrain");
 
 			foreach (var kv in tiles)
 			{
-				if (!cliprect.Contains(kv.Key.X, kv.Key.Y))
+				if (!wr.Viewport.VisibleCells.Contains(kv.Key))
 					continue;
 
 				if (wr.world.ShroudObscures(kv.Key))
diff --git a/OpenRA.Mods.RA/World/DomainIndex.cs b/OpenRA.Mods.RA/World/DomainIndex.cs
index 2e6dbdbf76..9b6704cca2 100644
--- a/OpenRA.Mods.RA/World/DomainIndex.cs
+++ b/OpenRA.Mods.RA/World/DomainIndex.cs
@@ -53,17 +53,17 @@ namespace OpenRA.Mods.RA
 
 	class MovementClassDomainIndex
 	{
-		Rectangle bounds;
+		Map map;
 
 		uint movementClass;
-		int[,] domains;
+		CellLayer<int> domains;
 		Dictionary<int, HashSet<int>> transientConnections;
 
 		public MovementClassDomainIndex(World world, uint movementClass)
 		{
-			bounds = world.Map.Bounds;
+			map = world.Map;
 			this.movementClass = movementClass;
-			domains = new int[(bounds.Width + bounds.X), (bounds.Height + bounds.Y)];
+			domains = new CellLayer<int>(world.Map);
 			transientConnections = new Dictionary<int, HashSet<int>>();
 
 			BuildDomains(world);
@@ -71,15 +71,15 @@ namespace OpenRA.Mods.RA
 
 		public bool IsPassable(CPos p1, CPos p2)
 		{
-			if (!bounds.Contains(p1.X, p1.Y) || !bounds.Contains(p2.X, p2.Y))
+			if (!map.Contains(p1) || !map.Contains(p2))
 				return false;
 
-			if (domains[p1.X, p1.Y] == domains[p2.X, p2.Y])
+			if (domains[p1] == domains[p2])
 				return true;
 
 			// Even though p1 and p2 are in different domains, it's possible
 			// that some dynamic terrain (i.e. bridges) may connect them.
-			return HasConnection(GetDomainOf(p1), GetDomainOf(p2));
+			return HasConnection(domains[p1], domains[p2]);
 		}
 
 		public void UpdateCells(World world, HashSet<CPos> dirtyCells)
@@ -90,22 +90,21 @@ namespace OpenRA.Mods.RA
 			{
 				// Select all neighbors inside the map boundries
 				var neighbors = CVec.directions.Select(d => d + cell)
-					.Where(c => bounds.Contains(c.X, c.Y));
+					.Where(c => map.Contains(c));
 
 				var found = false;
-				foreach (var neighbor in neighbors)
+				foreach (var n in neighbors)
 				{
-					if (!dirtyCells.Contains(neighbor))
+					if (!dirtyCells.Contains(n))
 					{
-						var neighborDomain = GetDomainOf(neighbor);
-
-						var match = CanTraverseTile(world, neighbor);
-						if (match) neighborDomains.Add(neighborDomain);
+						var neighborDomain = domains[n];
+						if (CanTraverseTile(world, n))
+							neighborDomains.Add(neighborDomain);
 
 						// Set ourselves to the first non-dirty neighbor we find.
 						if (!found)
 						{
-							SetDomain(cell, neighborDomain);
+							domains[cell] = neighborDomain;
 							found = true;
 						}
 					}
@@ -113,20 +112,8 @@ namespace OpenRA.Mods.RA
 			}
 
 			foreach (var c1 in neighborDomains)
-			{
 				foreach (var c2 in neighborDomains)
 					CreateConnection(c1, c2);
-			}
-		}
-
-		int GetDomainOf(CPos p)
-		{
-			return domains[p.X, p.Y];
-		}
-
-		void SetDomain(CPos p, int domain)
-		{
-			domains[p.X, p.Y] = domain;
 		}
 
 		bool HasConnection(int d1, int d2)
@@ -146,6 +133,7 @@ namespace OpenRA.Mods.RA
 				{
 					if (neighbor == d2)
 						return true;
+
 					if (!visited.Contains(neighbor))
 						toProcess.Push(neighbor);
 				}
@@ -180,7 +168,7 @@ namespace OpenRA.Mods.RA
 
 			var domain = 1;
 
-			var visited = new bool[(bounds.Width + bounds.X), (bounds.Height + bounds.Y)];
+			var visited = new CellLayer<bool>(map);
 
 			var toProcess = new Queue<CPos>();
 			toProcess.Enqueue(new CPos(map.Bounds.Left, map.Bounds.Top));
@@ -192,7 +180,7 @@ namespace OpenRA.Mods.RA
 
 				// Technically redundant with the check in the inner loop, but prevents
 				// ballooning the domain counter.
-				if (visited[start.X, start.Y])
+				if (visited[start])
 					continue;
 
 				var domainQueue = new Queue<CPos>();
@@ -205,7 +193,7 @@ namespace OpenRA.Mods.RA
 				while (domainQueue.Count != 0)
 				{
 					var n = domainQueue.Dequeue();
-					if (visited[n.X, n.Y])
+					if (visited[n])
 						continue;
 
 					var candidatePassable = CanTraverseTile(world, n);
@@ -215,12 +203,12 @@ namespace OpenRA.Mods.RA
 						continue;
 					}
 
-					visited[n.X, n.Y] = true;
-					SetDomain(n, domain);
+					visited[n] = true;
+					domains[n] = domain;
 
 					// Don't crawl off the map, or add already-visited cells
 					var neighbors = CVec.directions.Select(d => n + d)
-						.Where(p => bounds.Contains(p.X, p.Y) && !visited[p.X, p.Y]);
+						.Where(p => map.Contains(p) && !visited[p]);
 
 					foreach (var neighbor in neighbors)
 						domainQueue.Enqueue(neighbor);
diff --git a/OpenRA.Mods.RA/World/PathfinderDebugOverlay.cs b/OpenRA.Mods.RA/World/PathfinderDebugOverlay.cs
index ba6df9ce47..17cdcd7d50 100644
--- a/OpenRA.Mods.RA/World/PathfinderDebugOverlay.cs
+++ b/OpenRA.Mods.RA/World/PathfinderDebugOverlay.cs
@@ -11,6 +11,7 @@
 using System;
 using System.Collections.Generic;
 using System.Drawing;
+using OpenRA;
 using OpenRA.Graphics;
 using OpenRA.Primitives;
 using OpenRA.Traits;
@@ -20,7 +21,7 @@ namespace OpenRA.Mods.RA
 	class PathfinderDebugOverlayInfo : TraitInfo<PathfinderDebugOverlay> { }
 	class PathfinderDebugOverlay : IRenderOverlay, IWorldLoaded
 	{
-		Dictionary<Player, int[,]> layers;
+		Dictionary<Player, CellLayer<int>> layers;
 		int refreshTick;
 		World world;
 		public bool Visible;
@@ -29,7 +30,7 @@ namespace OpenRA.Mods.RA
 		{
 			world = w;
 			refreshTick = 0;
-			layers = new Dictionary<Player, int[,]>(8);
+			layers = new Dictionary<Player, CellLayer<int>>(8);
 
 			// Enabled via Cheats menu
 			Visible = false;
@@ -39,15 +40,15 @@ namespace OpenRA.Mods.RA
 		{
 			if (maxWeight == 0) return;
 
-			int[,] layer;
+			CellLayer<int> layer;
 			if (!layers.TryGetValue(pl, out layer))
 			{
-				layer = new int[world.Map.MapSize.X, world.Map.MapSize.Y];
+				layer = new CellLayer<int>(world.Map);
 				layers.Add(pl, layer);
 			}
 
 			foreach (var p in cellWeights)
-				layer[p.First.X, p.First.Y] = Math.Min(128, layer[p.First.X, p.First.Y] + (maxWeight - p.Second) * 64 / maxWeight);
+				layer[p.First] = Math.Min(128, layer[p.First] + (maxWeight - p.Second) * 64 / maxWeight);
 		}
 
 		public void Render(WorldRenderer wr)
@@ -59,29 +60,25 @@ namespace OpenRA.Mods.RA
 			var doDim = refreshTick - world.WorldTick <= 0;
 			if (doDim) refreshTick = world.WorldTick + 20;
 
-			var viewBounds = wr.Viewport.CellBounds;
 			foreach (var pair in layers)
 			{
 				var c = (pair.Key != null) ? pair.Key.Color.RGB : Color.PaleTurquoise;
 				var layer = pair.Value;
 
 				// Only render quads in viewing range:
-				for (var j = viewBounds.Top; j <= viewBounds.Bottom; ++j)
+				foreach (var cell in wr.Viewport.VisibleCells)
 				{
-					for (var i = viewBounds.Left; i <= viewBounds.Right; ++i)
-					{
-						if (layer[i, j] <= 0)
-							continue;
+					if (layer[cell] <= 0)
+						continue;
 
-						var w = Math.Max(0, Math.Min(layer[i, j], 128));
-						if (doDim)
-							layer[i, j] = layer[i, j] * 5 / 6;
+					var w = Math.Max(0, Math.Min(layer[cell], 128));
+					if (doDim)
+						layer[cell] = layer[cell] * 5 / 6;
 
-						// TODO: This doesn't make sense for isometric terrain
-						var tl = wr.ScreenPxPosition(new CPos(i, j).TopLeft);
-						var br = wr.ScreenPxPosition(new CPos(i, j).BottomRight);
-						qr.FillRect(RectangleF.FromLTRB(tl.X, tl.Y, br.X, br.Y), Color.FromArgb(w, c));
-					}
+					// TODO: This doesn't make sense for isometric terrain
+					var tl = wr.ScreenPxPosition(cell.TopLeft);
+					var br = wr.ScreenPxPosition(cell.BottomRight);
+					qr.FillRect(RectangleF.FromLTRB(tl.X, tl.Y, br.X, br.Y), Color.FromArgb(w, c));
 				}
 			}
 		}
diff --git a/OpenRA.Mods.RA/World/SmudgeLayer.cs b/OpenRA.Mods.RA/World/SmudgeLayer.cs
index a632b44379..f1c1e65e35 100644
--- a/OpenRA.Mods.RA/World/SmudgeLayer.cs
+++ b/OpenRA.Mods.RA/World/SmudgeLayer.cs
@@ -120,12 +120,11 @@ namespace OpenRA.Mods.RA
 
 		public void Render(WorldRenderer wr)
 		{
-			var cliprect = wr.Viewport.CellBounds;
 			var pal = wr.Palette("terrain");
 
 			foreach (var kv in tiles)
 			{
-				if (!cliprect.Contains(kv.Key.X, kv.Key.Y))
+				if (!wr.Viewport.VisibleCells.Contains(kv.Key))
 					continue;
 
 				if (world.ShroudObscures(kv.Key))
diff --git a/OpenRA.Utility/LegacyMapImporter.cs b/OpenRA.Utility/LegacyMapImporter.cs
index e1a5aa359e..ded0b9d2ab 100644
--- a/OpenRA.Utility/LegacyMapImporter.cs
+++ b/OpenRA.Utility/LegacyMapImporter.cs
@@ -137,6 +137,7 @@ namespace OpenRA.Utility
 			var width = Exts.ParseIntegerInvariant(mapSection.GetValue("Width", "0"));
 			var height = Exts.ParseIntegerInvariant(mapSection.GetValue("Height", "0"));
 			mapSize = (legacyMapFormat == IniMapFormat.RedAlert) ? 128 : 64;
+			var size = new Size(mapSize, mapSize);
 
 			map.Title = basic.GetValue("Name", Path.GetFileNameWithoutExtension(iniFile));
 			map.Author = "Westwood Studios";
@@ -148,8 +149,8 @@ namespace OpenRA.Utility
 
 			map.Smudges = Exts.Lazy(() => new List<SmudgeReference>());
 			map.Actors = Exts.Lazy(() => new Dictionary<string, ActorReference>());
-			map.MapResources = Exts.Lazy(() => new TileReference<byte, byte>[mapSize, mapSize]);
-			map.MapTiles = Exts.Lazy(() => new TileReference<ushort, byte>[mapSize, mapSize]);
+			map.MapResources = Exts.Lazy(() => new CellLayer<ResourceTile>(size));
+			map.MapTiles = Exts.Lazy(() => new CellLayer<TerrainTile>(size));
 
 			map.Options = new MapOptions();
 
@@ -250,20 +251,20 @@ namespace OpenRA.Utility
 
 		void UnpackRATileData(MemoryStream ms)
 		{
-			for (var i = 0; i < mapSize; i++)
-				for (var j = 0; j < mapSize; j++)
-					map.MapTiles.Value[i, j] = new TileReference<ushort, byte>();
-
+			var types = new ushort[mapSize, mapSize];
 			for (var j = 0; j < mapSize; j++)
+			{
 				for (var i = 0; i < mapSize; i++)
 				{
 					var tileID = ms.ReadUInt16();
-					map.MapTiles.Value[i, j].Type = tileID == (ushort)0 ? (ushort)255 : tileID; // RAED weirdness
+					types[i, j] = tileID == (ushort)0 ? (ushort)255 : tileID; // RAED weirdness
 				}
+			}
 
 			for (var j = 0; j < mapSize; j++)
 				for (var i = 0; i < mapSize; i++)
-					map.MapTiles.Value[i, j].Index = ms.ReadUInt8();
+					map.MapTiles.Value[new CPos(i, j)] = new TerrainTile(types[i, j], ms.ReadUInt8());
+
 		}
 
 		void UnpackRAOverlayData(MemoryStream ms)
@@ -277,15 +278,16 @@ namespace OpenRA.Utility
 
 					if (o != 255 && overlayResourceMapping.ContainsKey(redAlertOverlayNames[o]))
 						res = overlayResourceMapping[redAlertOverlayNames[o]];
-
-					map.MapResources.Value[i, j] = new TileReference<byte, byte>(res.First, res.Second);
+					
+					var cell = new CPos(i, j);
+					map.MapResources.Value[cell] = new ResourceTile(res.First, res.Second);
 
 					if (o != 255 && overlayActorMapping.ContainsKey(redAlertOverlayNames[o]))
 					{
 						map.Actors.Value.Add("Actor" + actorCount++,
 							new ActorReference(overlayActorMapping[redAlertOverlayNames[o]])
 							{
-								new LocationInit(new CPos(i, j)),
+								new LocationInit(cell),
 								new OwnerInit("Neutral")
 							});
 					}
@@ -313,16 +315,13 @@ namespace OpenRA.Utility
 
 		void UnpackCncTileData(Stream ms)
 		{
-			for (var i = 0; i < mapSize; i++)
-				for (var j = 0; j < mapSize; j++)
-					map.MapTiles.Value[i, j] = new TileReference<ushort, byte>();
-
 			for (var j = 0; j < mapSize; j++)
 			{
 				for (var i = 0; i < mapSize; i++)
 				{
-					map.MapTiles.Value[i, j].Type = ms.ReadUInt8();
-					map.MapTiles.Value[i, j].Index = ms.ReadUInt8();
+					var type = ms.ReadUInt8();
+					var index = ms.ReadUInt8();
+					map.MapTiles.Value[new CPos(i, j)] = new TerrainTile(type, index);
 				}
 			}
 		}
@@ -342,7 +341,7 @@ namespace OpenRA.Utility
 				if (overlayResourceMapping.ContainsKey(kv.Value.ToLower()))
 					res = overlayResourceMapping[kv.Value.ToLower()];
 
-				map.MapResources.Value[cell.X, cell.Y] = new TileReference<byte, byte>(res.First, res.Second);
+				map.MapResources.Value[cell] = new ResourceTile(res.First, res.Second);
 
 				if (overlayActorMapping.ContainsKey(kv.Value.ToLower()))
 					map.Actors.Value.Add("Actor" + actorCount++,