Here is the data folder for TST, a rebuilt map I found in the files of the GOG version of the game. I unmunged the test1.lvl found inside data/_lvl_pc/Test/ in order to build it.
It is "Sky to Ground" in that there are two venators and a terrain. The highest one is right below 999 meters. There are also some interesting light regions on the ground as well as several vehicle spawns where they seemingly tested them. This isn't a finished, perfectly playable map, but it seems it's a simple testing map Pandemic used during development. It's for sure interesting to look and see what they were playing with!
Link: http://www.mediafire.com/file/i4nv4isic ... T.exe/file
