GM_CircleTower by Biotoxsin is a superstructure with five different levels: concrete, snow, grass, dirt, and the bottom level, with sand and water.
Each level features a room with teleporters to help you quickly travel to the other levels of the map.
The map was originally started two years ago, but was finally completed about two weeks ago. It boasts custom textures for all of the level's main surfaces.
The map author says he's going to make more releases of this map, so be sure to keep your eye on his topic!
Download it here:
For more information, and to get some help or support, check out this map's forum thread.[...]