Mars City Underground: Level 2 of the Doom 3 Walkthrough

Exit the lift and talk to the marine stationed in the booth on your right. He’ll direct you to grab some armor and a pistol from the glass case on your right and then test your radio before letting you pass through the door. You’ll receive a new objective on your PDA to go to the Old Comm Building. Follow the walkway round to the right and head down the stairs before entering the door with the Energy Stabilization sign above it. Head down the stairs and you’ll find a slimy looking guy on your left hiding behind a box who will talk to you. Once he’s done head through the door and along the corridor, you’ll find a PDA to pick up on your left. The PDA has a code (531) which will allow you to open the cabinet. Once you’re done head through the door and in the chamber beyond take the door on your left.

Take the next door on your left and as you enter the lights will fail so tap F to bring up your flashlight and head down the stairs. Go through the door and down into the loading bay where the marine will tell you that you need to head outside to reach the Comm Building. Pick up the gun and ammo on the crate and hit the yellow airlock release button. Get into the airlock and hit the button so it opens and then walk across the bridge, pausing to admire the scenery of Mars. Activate the airlock on the other side in the same way and head inside. You’ll find a medkit on the right if you need it, take the stairs and then the lift up to Communications on level 2. Once the lift stops exit and follow the corridor round and you’ll trigger a new cut scene.

After the cut scene things turn a little scary and the scientist will disappear. The door you came through will open and you should kill the zombie who pops up and then proceed back to the lift, killing another zombie along the way. Go back down in the lift and grab the medkit in the room at the bottom if you need it. Head back into the airlock and outside across the bridge and back into the other airlock. There will be a zombie on your right when you come out of the airlock. Head up the stairs and behind the next door there will be another zombie waiting for you. Take him out and continue up the stairs and then through the next door there will be another zombie climbing up on your right, kill him and then activate the panel in front of you which will deploy a bridge. Cross the bridge and kill the z-sec at the end of the corridor and the one waiting through the next door.