Site 3 is the ground level access point to he original subterranean Mars structure. Research objects from the lower levels are analyzed and studied in this facility.

Your health mat be low as you come out of the elevator, so turn left and bring it up to 100 using the emergency medical station. As you walk forward, the screen will turn red, and you will see a hell knight emerge from the floor. Kill him, and turn around - there will be a wraith behind you. TIP: you can shoot wraiths even when you can't see them; they don't teleport, they just become invisible. An imp will appear behind you. After he is dead, another wraith will spawn. Continue down the hallway.

At the end, if you approach the door on the right, you will gain a new objective: gain security clearance for all Site 3 areas. Turn around and go through the other door. An imp will spawn behind you as you walk through, on your left. 2 cacodemons will spawn inside the room. Use caution, there are explosive barrels that can get you killed since all three demons (and you) are hurling things that can blow them up.

Go into the room: a hell knight will spawn. Same warning about the barrels applies. Kill him, and grab the clip, 2 boxes of shells and 2 plasma canisters off the shelves. The door at the back is locked (though there is an emergency medical station nearby with 100 health), so go into the door labelled "Garage". Two wraiths and a a cacodemon await. If your health is low, another emergency medical station is on your left with 75 health in it.

Go down the stairs. A hell knight will spawn ahead of you, kill him and go for the shelves with 5 plasma canisters, an ammo belt, 50 armor and a box of shells. Turn left, go through the door. As you walk in, the area to your right will turn from a garage into a demonic spawn site (candles included!). An arch-vile will spawn. If you kill him quickly, he'll only spawn one other creature, perhaps an imp. Finish killing everything, and cross the room to the door on the opposite side. If you need it, there is 30 health on the left and some armor shards behind the stairs you go up to get to the door.

Go through the door. You'll hear a revenant nearby; he's up the stairs. Kill him, but watch out for the 2 headed demon and imp that spawn below. You can go into the lower area and pick up the clip and ammo belt. The go up the stairs, through the door, killing the wraith. You'll see a ladder. Down down.

At the bottom, you'll walk out into a hallway, and you'll hear some spawning. On the left: a two headed demon. On the right, an imp. Go either way (they both lead to the same room), and you'll see an imp up on the walkway. Kill him, and another will spawn by the main screen. Kill him and grab the PDA of Richard Davis. There's also 30 health on the shelf to your left. Proceed along the walkway you saw the first imp on. Go up the stairs and through the door. Walk through it and you'll hear another revenant. He's at the end of the hall, to your right. Kill him, and the two headed demon with him. An imp will spawn. Kill him as well.

Don't go straight. Turn left and kill the imp in the next hallway on your left. If you need it, grab the 2 15 health packs and 50 armor dead ahead. Turn left and you'll see a ladder. Go up and follow the duct. Stick the right side as you jump down (to break your fall) and crouch to get out into the next room.

Go past the stairs on the right and pick up the 50 armor and grenades. 3 simultaneous spawns: hell knight and 2 of the 2 headed demons. Kill them, and go to the office in the corner. After hearing the scientists speech, grab the PDA (Pierce Rogers) and video disk inside. Also on the shelf are an ammo belt and 3 plasma canisters. Next to it is an emergency medical station with 75 health. Stock up and head out.

New objective: locate the freight loader control tower to unlock the entrance to the caverns. As you leave, an arch-vile will spawn. Kill him and move the middle of the room. Five (5!) 2-headed demons will spawn along with an imp. Mow them down and head for the security locked door. Scan your PDA to get through, and you'll see you come out near the ladder you climbed earlier. Go right, kill the revenant, and then make a quick left and go to the end of the hall. Scan your PDA to get through the door. You're back in another familiar area near where you started, but kill the imp before you look around.

Go straight across the hall through the next door. This will trigger 2 spawns: one to your left down the hall (an imp) and one inside the room (a revenant). Kill both and go past the garage to the locked door on the other side. Open it, and kill the 2 headed demon in front of you (near the elevator) and the imp behind you and above you to your left. Then turn right, go down the ladder (use flashlight) and grab the armor and box of shells from the shelf. Go back up the ladder and take the elevator up to maintenance.

Double attack by a wraith and a 2 headed demon as you come out of the elevator. Turn right, through the door, and go up the stairs. Follow the tunnel until you come out in a hallway. Kill the revenant behind the door to your left, and the imp coming down the hallway on your right. In the room with the revenant is 3 plasma canisters. Go down the hall and up the stairs. Follow the path, go up the next set, and a cacodemon will spawn near the flames. Kill him, proceed until you see a door.

Step through and kill the imp, and the cacodemon that spawned behind you. Go inside, grab the clip, shells, and 50 armor on the shelf to your left, and the 3 plasma canisters, BFG cell and plasma gun ahead. Make a right and go through the door. Go inside, down the ladder, and use the computer to unlock the entrance to the caverns. Go back up the ladder and retrace your steps. Two cacodemons will spawn in the room with the pit of fire. Go down the stairs, and the floor panels will fall in front of you. Drop down and follow the path. You'll get ambushed by 2 wraiths and an imp. Grab the 15 health pack in the area to the right, and go into the tunnel of blood/flesh ahead. You'll drop out into a familiar area. Turn left, go through the door, and head into the garage. Kill the imp that spawns behind you and go up the stairs on the other side of the garage to get into the freight loader. Press the button to transfer the freight loader. Once you get there, you will see an elevator. Go around behind it and pick up the 3 clips, 2 plasma canisters, 15 health pack and 50 armor. Go back around and use the elevator to go down to Caverns Area 1.