//	if (!IsTileFlat(tile) || !IsTileFlat(tile2)) {
//		int z_slope1;
//		Slope slope1 = GetTileSlope(tile, &z_slope1);
//		int z_middle_corner_n = TileHeight(tile2);
//		int z_middle_corner_s = TileHeight(TileAddByDiagDir(tile2, AxisToDiagDir(OtherAxis(axis))));
//		int z_slope2;
//		Slope slope2 = GetTileSlope(tile2, &z_slope2);

//		/* Forbid these combinations. */
		/**
		 *       3
		 *      / \
		 *     2   2
		 *    / \ /
		 *   1   1
		 *    \ /
		 *     0
		 */
//		if (IsSteepSlope(slope1) || IsSteepSlope(slope2)) return_cmd_error(STR_ERROR_SITE_UNSUITABLE);

	    /**
		 *       1
		 *      / \
		 *     0   0
		 *    / \ /
		 *   1   1
		 *    \ /
		 *     0
		 */
//		if (slope1 == SLOPE_NS && slope2 == SLOPE_EW || slope1 == SLOPE_EW && slope2 == SLOPE_NS) return_cmd_error(STR_ERROR_SITE_UNSUITABLE);

	    /**
		 *       1
		 *      / \
		 *     0   1
		 *    / \ /
		 *   0   1
		 *    \ /
		 *     0
		 */
//		if (z_middle_corner_n != z_middle_corner_s && (IsSlopeWithThreeCornersRaised(slope1) && IsSlopeWithOneCornerRaised(slope2) || IsSlopeWithOneCornerRaised(slope1) && IsSlopeWithThreeCornersRaised(slope2))) return_cmd_error(STR_ERROR_SITE_UNSUITABLE);

		/**
		 *       2
		 *      / \
		 *     1   2
		 *    / \ /
		 *   0   1
		 *    \ /
		 *     0
		 */
//		if (slope1 == slope2 && IsInclinedSlope(slope1)) return_cmd_error(STR_ERROR_SITE_UNSUITABLE);

		/**
		 *       1
		 *      / \
		 *     0   1
		 *    / \ /
		 *   0   0
		 *    \ /
		 *     1
		 */
//		if (((IsSlopeWithOneCornerRaised(slope2) || IsSlopeWithThreeCornersRaised(slope2)) && IsInclinedSlope(slope1) && DiagDirToAxis(GetInclinedSlopeDirection(slope1)) == axis) || ((IsSlopeWithOneCornerRaised(slope1) || IsSlopeWithThreeCornersRaised(slope1)) && IsInclinedSlope(slope2) && DiagDirToAxis(GetInclinedSlopeDirection(slope2)) == axis)) return_cmd_error(STR_ERROR_SITE_UNSUITABLE);

		/**
		 *       0
		 *      / \
		 *     0   1
		 *    / \ /
		 *   1   1
		 *    \ /
		 *     0
		 */
//		if (((slope2 == SLOPE_EW || slope2 == SLOPE_NS) && IsInclinedSlope(slope1) && DiagDirToAxis(GetInclinedSlopeDirection(slope1)) == OtherAxis(axis)) || ((slope1 == SLOPE_EW || slope1 == SLOPE_NS) && IsInclinedSlope(slope2) && DiagDirToAxis(GetInclinedSlopeDirection(slope2)) == OtherAxis(axis))) return_cmd_error(STR_ERROR_SITE_UNSUITABLE);