Mars City: Union Aerospace Corporate Division


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Doom 3 maps
Map name: game/mars_city2
"Marine? I can't believe you're still alive."
― Sergeant Kelly [source]

Mars City: Union Aerospace Corporate Division is the third level of Doom 3. The same level as Mars City, but after the demon invasion. The marine is given his mission to link up with Bravo Team in this level. This is where the demo ends.


Spoiler Warning: Plot details follow.

The Player returns to Mars City to find the place in chaos. The sounds of battle can be heard coming from the walls, but at this point, most of Mars City has already fallen.

Fairly early in the level, the Player encounters a survivor Roland who is hiding in the ventilation shaft near the elevator. Roland extends a ladder, allowing the Player to climb into the shaft. He then urges the Player to go get help.

The Player uses the ventilation shaft to enter the Manifest Control Office, and from there, fights his way through Security Operations to the Infirmary. From there, he gains access to Marine Command and arrives back at Marine HQ. All the marines stationed there are dead, but a communications console is still working and has an incoming transmission from Sergeant Kelly, who is pleasantly surprised to see you're still alive.

Sergeant Kelly informs the Player that he is trapped in the Delta Complex and has decided to set up a command post there. He orders the Player to link up with Bravo Team and help them send a distress call to the Earth Fleet. In order to reach Bravo Team, the Player must head through Alpha Labs. Kelly also updates the Player's security clearance, giving him access to the ACO section of Mars City.

With the aid of a surviving Sentry Bot, the Player fights his way through the ACO area to the elevator. From there, he rides the elevator to the next level: Administration.

Spoilers end here.


After the elevator ride, you are given the order to regroup at Marine HQ. When you exit, there is one zombie attacking from behind the crate ahead of you. Approach the Storage Cabinet, and ascend. In the tunnel, follow the left-hand wall, picking up the armor, and gop through the burst pipes. The end of the ventilation shaft leads to the Manifest Control Office.

Once in the office, defeat the enemies, and exit the door. Take the right door first to get the ACO Key Card.

In Sec Ops processing, the exit of this dark room is on the opposite side of the room.

Marine Command is found after the infirmary. If you want to go past a burning pipe for a PDA, you have to duck under it. To head to the HQ, instead take a right turn, and head to the end of the corridor. Approach the console asking for the video link up. You will receive instructions here, although if you've seen it before, you can spend time unlocking the supply cabinet and armory.

When you reach the central area, take a left. There are plenty of Z-Sec waiting here, but they are easily handled. The only available route leads to the ACO Lift Junction, which you can use to transfer to the next map. However, you can enter the service access tunnel on the right of the room to reach the last PDA, which can open a locked room just outside the lift.



Former Humans[edit]



  • Marcus Stanton: Found in Manifest Control Office
  • Marcus Caseon: Found in Infirmaty
  • Bill Tyson: Found in Marine Command, in corridor behind flaming pipe.
  • Duncan Mathews: Found in ACO Lift Junction. Requires going through a service access on the right of the room.


Cabinets/Door Codes[edit]

  • Cabinet #017: 347. Learned from Marcus Caseon's second audio log.
  • Mars City Armory: 584. Learned from Bill Tyson's PDA.


  • If you go into the bathroom and look at yourself in the mirror, you will see a vision of yourself turning into a zombie. When the vision ends, an Imp will spawn outside.
  • In the Demo version, when you complete the level, your vision will turn red and evil laughter will be heard.

External links[edit]

  • Walkthrough video by WoopzillaWalkthrough (part 1; part 2) on YouTube. Veteran difficulty; part of a full game run.