This article about a map is a stub. Please help the Doom Wiki by adding to it.

Doom 3 maps

Mars City Underground - "The Mars City Sublevel was one of the first multi-purpose installations built on Mars. Housing storage, environment systems, localized energy production, communications arrays, and rudimentary research systems, the aging facility is vital to keeping Mars City operational."

Mars City Underground: Union Aerospace Subsystems is the second level of Doom 3, composed of the main area and an abandoned communications facility separated by a short walk outside. It is a small tutorial level covering a few more features in the game.

In the Communications Facility, things start to go awry. The action begins here, and zombies are first seen. The Imp is introduced at a cutscene.


  • Underground Access
  • Underground Security
  • Underground Junction
  • Maintenance Area CS1
  • Convergence Chamber 1
  • Energy Stabilization Unit
  • Convergence Chamber 2
  • Energy Processing
  • Energy Delivery
  • Maintenance PD1
  • Underground Garage




Monster Count
Imp 7
Zombie 14/14/15
Pistol Z-Sec 3
Shotgun Z-Sec 3/3/4
Weapon Count
Flashlight 1
Pistol 1
Shotgun 4
Machine Gun 2
Ammunition Count
Pistol ammo (small) 15/15/13
Shotgun shells (small) 13
Shotgun shells (large) 2/2/1
Machine Gun ammo (small) 2
Machine Gun ammo (large) 1
Plasma cells (small) 2
Misc. items Count
Adrenaline 1
Small medkit 23/23/15
Large medkit 2
Armor shard 83/83/73
Security armor 3
  • For cells of the form x/y/z, x corresponds to Recruit difficulty, y to Marine, and z to Veteran/Nightmare.
  • Items that can only be acquired by using console commands are excluded.

Valve 1 Failure Code in Energy Processing: 842 (This will cause the fire to be extinguished and you will gain access to armor shards and ammo.)

Cabinet Codes

  • Storage Cabinet #023: Supplies - 531


  • In the beginning of the level before the demon invasion begins, if you use the noclip cheat around certain areas, you will get to see Zombies, Z-Secs, and Imps.
  • You may rescue the scientist in the Processing Unit area; he says "Oh, thank you. I'm getting out of here" and disappears through a door. Later, you will see an opened storage cabinet. If the scientist is killed, this cabinet will be closed.

Ad blocker interference detected!

Wikia is a free-to-use site that makes money from advertising. We have a modified experience for viewers using ad blockers

Wikia is not accessible if you’ve made further modifications. Remove the custom ad blocker rule(s) and the page will load as expected.