--- a/src/industry_cmd.cpp	Thu Jun 12 19:06:30 2008 +0000
+++ b/src/industry_cmd.cpp	Thu Jun 12 21:36:56 2008 +0000
@@ -337,8 +337,7 @@
 	IndustryGfx gfx = GetIndustryGfx(tile);
 
 	/* For NewGRF industry tiles we might not be drawing a foundation. We need to
-	 * account for this, otherwise we might be applying a FOUNDATION_LEVELED
-	 * on a steep slope which is not allowed. Furthermore other structures should
+	 * account for this, as other structures should
 	 * draw the wall of the foundation in this case.
 	 */
 	if (gfx >= NEW_INDUSTRYTILEOFFSET) {

--- a/src/landscape.cpp	Thu Jun 12 19:06:30 2008 +0000
+++ b/src/landscape.cpp	Thu Jun 12 21:36:56 2008 +0000
@@ -79,8 +79,9 @@
 	if (!IsFoundation(f)) return 0;
 
 	if (IsLeveledFoundation(f)) {
+		uint dz = TILE_HEIGHT + (IsSteepSlope(*s) ? TILE_HEIGHT : 0);
 		*s = SLOPE_FLAT;
-		return TILE_HEIGHT;
+		return dz;
 	}
 
 	if (f != FOUNDATION_STEEP_BOTH && IsNonContinuousFoundation(f)) {
@@ -402,6 +403,9 @@
 
 			AddSortableSpriteToDraw(inclined_base + inclined, PAL_NONE, ti->x, ti->y, 16, 16, 1, ti->z);
 			OffsetGroundSprite(31, 9);
+		} else if (IsLeveledFoundation(f)) {
+			AddSortableSpriteToDraw(leveled_base + SlopeWithOneCornerRaised(highest_corner), PAL_NONE, ti->x, ti->y, 16, 16, 7, ti->z - TILE_HEIGHT);
+			OffsetGroundSprite(31, 1);
 		} else if (f == FOUNDATION_STEEP_LOWER) {
 			/* one corner raised */
 			OffsetGroundSprite(31, 1);

--- a/src/slope_func.h	Thu Jun 12 19:06:30 2008 +0000
+++ b/src/slope_func.h	Thu Jun 12 21:36:56 2008 +0000
@@ -347,13 +347,11 @@
  * Returns the foundation needed to flatten a slope.
  * The returned foundation is either FOUNDATION_NONE if the tile was already flat, or FOUNDATION_LEVELED.
  *
- * @pre      The slope must not be steep.
  * @param s  The current #Slope.
  * @return   The needed #Foundation.
  */
 static inline Foundation FlatteningFoundation(Slope s)
 {
-	assert(!IsSteepSlope(s));
 	return (s == SLOPE_FLAT ? FOUNDATION_NONE : FOUNDATION_LEVELED);
 }