--- a/src/tilearea_type.h
+++ b/src/tilearea_type.h
@@ -60,10 +60,37 @@
 	}
 };
 
-/** Iterator to iterate over a tile area (rectangle) of the map. */
+/** Base class for tile iterators. */
 class TileIterator {
+protected:
+	TileIndex tile; ///< The current tile we are at.
+
+	/**
+	 * Initialise the iterator starting at this tile.
+	 * @param tile The tile we start iterating from.
+	 */
+	TileIterator(TileIndex tile) : tile(tile)
+	{
+	}
+public:
+	/**
+	 * Get the tile we are currently at.
+	 * @return The tile we are at, or INVALID_TILE when we're done.
+	 */
+	FORCEINLINE operator TileIndex () const
+	{
+		return this->tile;
+	}
+
+	/**
+	 * Move ourselves to the next tile in the rectange on the map.
+	 */
+	virtual TileIterator& operator ++() = 0;
+};
+
+/** Iterator to iterate over a tile area (rectangle) of the map. */
+class OrthogonalTileIterator : public TileIterator {
 private:
-	TileIndex tile; ///< The current tile we are at.
 	int w;          ///< The width of the iterated area.
 	int x;          ///< The current 'x' position in the rectangle.
 	int y;          ///< The current 'y' position in the rectangle.
@@ -73,18 +100,8 @@
 	 * Construct the iterator.
 	 * @param ta Area, i.e. begin point and width/height of to-be-iterated area.
 	 */
-	TileIterator(const TileArea &ta) : tile(ta.tile), w(ta.w), x(ta.w), y(ta.h)
+	OrthogonalTileIterator(const TileArea &ta) : TileIterator(ta.w == 0 || ta.h == 0 ? INVALID_TILE : ta.tile), w(ta.w), x(ta.w), y(ta.h)
 	{
-		if (ta.w == 0 || ta.h == 0) this->tile = INVALID_TILE;
-	}
-
-	/**
-	 * Get the tile we are currently at.
-	 * @return The tile we are at, or INVALID_TILE when we're done.
-	 */
-	FORCEINLINE operator TileIndex () const
-	{
-		return this->tile;
 	}
 
 	/**
@@ -112,6 +129,6 @@
  *            This variable will be allocated in this \c for of this loop.
  * @param ta  The tile area to search over.
  */
-#define TILE_AREA_LOOP(var, ta) for (TileIterator var(ta); var != INVALID_TILE; ++var)
+#define TILE_AREA_LOOP(var, ta) for (OrthogonalTileIterator var(ta); var != INVALID_TILE; ++var)
 
 #endif /* TILEAREA_TYPE_H */