Mars City Underground: Union Aerospace Subsystems

From Doom Wiki

Doom 3 maps
Mars City: Intro 1 2 3 Alpha Labs: 1 2 3 4 Enpro Communications: 1 2 Monorail/Recycling: 1 2 3 Delta Labs: 1 2a 2b 3 4 Hell Delta Complex Central Processing: 1 2 Excavation: 1 2 3 End

Mars City Underground: Union Aerospace Subsystems is the second level of Doom 3. A shorter tutorial covering a few more features in the game. In the Communications Building, things start to go awry. The shooting begins here. The imp is introduced at a cutscene.