diff --git a/src/c3nav/mapdata/render/geometry/altitudearea.py b/src/c3nav/mapdata/render/geometry/altitudearea.py
index f4b98b2c..96cee108 100644
--- a/src/c3nav/mapdata/render/geometry/altitudearea.py
+++ b/src/c3nav/mapdata/render/geometry/altitudearea.py
@@ -42,8 +42,11 @@ class AltitudeAreaGeometries:
                                                                        faces_offset, vertices_offset)
 
         for key in tuple(self.obstacles.keys()):
-            faces_offset, vertices_offset = self._call_create_full(self.obstacles, key, faces, vertices,
-                                                                   faces_offset, vertices_offset)
+            height_obstacles = list(self.obstacles[key])
+            for i in range(len(height_obstacles)):
+                faces_offset, vertices_offset = self._call_create_full(height_obstacles, i, faces, vertices,
+                                                                       faces_offset, vertices_offset)
+            self.obstacles[key] = tuple(height_obstacles)
 
         if not vertices:
             return np.empty((0, 2), dtype=np.int32), np.empty((0, 3), dtype=np.uint32)
@@ -90,8 +93,9 @@ class AltitudeAreaGeometries:
                                       lower=altitudes,
                                       upper=altitudes + int(0.001 * 1000),
                                       crops=crops)
-        for height, geometry in self.obstacles.items():
-            geometry.build_polyhedron(create_polyhedron,
-                                      lower=altitudes,
-                                      upper=altitudes + height,
-                                      crops=crops)
+        for height, height_geometries in self.obstacles.items():
+            for geometry in height_geometries:
+                geometry.build_polyhedron(create_polyhedron,
+                                          lower=altitudes,
+                                          upper=altitudes + height,
+                                          crops=crops)
diff --git a/src/c3nav/mapdata/render/geometry/level.py b/src/c3nav/mapdata/render/geometry/level.py
index 41319308..84282a65 100644
--- a/src/c3nav/mapdata/render/geometry/level.py
+++ b/src/c3nav/mapdata/render/geometry/level.py
@@ -148,9 +148,6 @@ class LevelGeometries:
             for access_restriction, areas in tuple(color_group.items()):
                 color_group[access_restriction] = unary_union(areas)
 
-        # merge obstacles
-        obstacles = {key: unary_union(polygons) for key, polygons in obstacles.items()}
-
         # add altitudegroup geometries and split ground colors into them
         for altitudearea in level.altitudeareas.all():
             altitudearea_prep = prepared.prep(altitudearea.geometry)
@@ -160,9 +157,13 @@ class LevelGeometries:
                                    for color, areas in colors.items()}
             altitudearea_colors = {color: areas for color, areas in altitudearea_colors.items() if areas}
 
-            altitudearea_obstacles = {height: area.intersection(altitudearea.geometry)
-                                      for height, area in obstacles.items()
-                                      if altitudearea_prep.intersects(area)}
+            altitudearea_obstacles = {height: tuple(obstacle.intersection(altitudearea.geometry)
+                                                    for obstacle in height_obstacles
+                                                    if altitudearea_prep.intersects(obstacle))
+                                      for height, height_obstacles in obstacles.items()}
+            altitudearea_obstacles = {height: height_obstacles
+                                      for height, height_obstacles in obstacles.items()
+                                      if height_obstacles}
             geoms.altitudeareas.append(AltitudeAreaGeometries(altitudearea,
                                                               altitudearea_colors,
                                                               altitudearea_obstacles))
diff --git a/src/c3nav/mapdata/render/renderdata.py b/src/c3nav/mapdata/render/renderdata.py
index c684969a..1c68dff3 100644
--- a/src/c3nav/mapdata/render/renderdata.py
+++ b/src/c3nav/mapdata/render/renderdata.py
@@ -189,9 +189,13 @@ class LevelRenderData:
                             new_colors[color] = new_areas
                     new_altitudearea.colors = new_colors
 
-                    new_altitudearea.obstacles = {key: new_geometry.intersection(areas)
-                                                  for key, areas in altitudearea.obstacles.items()
-                                                  if new_geometry_prep.intersects(areas)}
+                    new_altitudearea.obstacles = {key: tuple(new_geometry.intersection(obstacle)
+                                                             for obstacle in height_obstacles
+                                                             if new_geometry_prep.intersects(obstacle))
+                                                  for key, height_obstacles in altitudearea.obstacles.items()}
+                    new_altitudearea.obstacles = {height: height_obstacles
+                                                  for height, height_obstacles in new_altitudearea.obstacles.items()
+                                                  if height_obstacles}
 
                     new_geoms.altitudeareas.append(new_altitudearea)
 
diff --git a/src/c3nav/mapdata/render/renderer.py b/src/c3nav/mapdata/render/renderer.py
index 1bcd7b96..15a62846 100644
--- a/src/c3nav/mapdata/render/renderer.py
+++ b/src/c3nav/mapdata/render/renderer.py
@@ -105,9 +105,10 @@ class MapRenderer:
 
             # add obstacles after everything related to ground for the nice right order
             for i, altitudearea in enumerate(geoms.altitudeareas):
-                for height, obstacle in altitudearea.obstacles.items():
-                    engine.add_geometry(obstacle, fill=FillAttribs('#B7B7B7'),
-                                        stroke=StrokeAttribs('#888888', 0.05, min_px=0.2), category='obstacles')
+                for height, height_obstacles in altitudearea.obstacles.items():
+                    for obstacle in height_obstacles:
+                        engine.add_geometry(obstacle, fill=FillAttribs('#B7B7B7'),
+                                            stroke=StrokeAttribs('#888888', 0.05, min_px=0.2), category='obstacles')
 
             # add walls, stroke_px makes sure that all walls are at least 1px thick on all zoom levels,
             walls = None