- This level occupies the map slot MAP03. For other maps which occupy this slot, see Category:MAP03.
MAP03: Main Engineering is the third level of Doom 64. The level is relatively small, consisting of only four small rooms where you need to activate teleporters or press switches to receive keys, yet each room is populated with plentiful amounts of monsters, leading to quick and intense battles. It uses the music track "Tortured Transmission" by Aubrey Hodges. The level also introduces Cacodemons, Lost Souls and a brand new enemy exclusive to Doom 64: the Nightmare Imp.
Main Engineering is unique in that two of the rooms' structures end up changing either moderately (the center room with the blue key) or dramatically (the second to last room, where the player finds the switch which gives him access to the red key).
Kill the Shotgun guy in front of you and press the switch to open the doors at both sides of you. The surrounding floor contains several Nightmare imps. Pass the door in the middle and enter the room carefully. Wait until the central podest built up and walls to your sides opened - revealing more normal and nightmare imps. Get the blue key on top of the podest. Some ammo clips and stimpacks are available in the teleporter corners.
Pass the blue door, face several Nightmare imps and Cacodemons, and activate at least either one of the teleporters in the corners of the central building by pressing switches in its side walls. You will appear on the upper railing where you can find stimpacks in the corners. Getting them opens closets at the ends with a stimpack and a box of shotgun shells, or a box of ammo on the other side. A switch in the center appears with more ammo in front of; as if you would need it. Pressing the switch opens the central room and releases more Cacodemons and Lost souls. The yellow key is contained inside, a lift is available at the entrance side after cleaning the room from all monsters. You may return to the starting point to find a Backpack there.
Return to the podest where the blue key was kept (more normal and nightmare imps await you) and pass the yellow door straight up, taking a Chaingun and a Box of bullets. More Nightmare imps welcome you in the entrance where you obviously need to press a switch, trying to get to rows of Health bonuses and Armor bonuses. The ceiling lowers and appears to crush a bassin into the floor. A step forward, and Imps and Lost souls appear.
After finishing them off, descend into the bassin. The right switch briefly opens a niche with Stimpacks and Boxes of rockets opposite to the entrance. Pressing the left switch has no obvious result yet. Return to the previous room and find the red key on the podest. Enter the corridor behind the red door to find more Nightmare imps and the Exit switch.
- After the podest with the blue key built up and the walls opened to staircases, hug the outer wall of the right staircase to find a secret area with a Partial Invisibility sphere behind a fake wall near its middle corner.
- Do the same for the left staircase to find an Invulnerability sphere at its top.
- In the room behind the blue door, touch the red glowing computer which opens a closet containing a Berserk pack, a Chainsaw and a box of shotgun shells
- After entering the yellow room and killing every Imp and Lost Soul, there are two switches, the one on the left opens the closet up ahead containing various types of ammunition. Upon entering, a door in the bottom right corner of the yellow room opens. Rush to it where you'll be granted a lot of different ammunition.
- After killing all the Nightmare Imps in the red room, the green glowing screen that faces the exit switch is a secret switch itself. Pressing it opens a closet containing Mega Armor in the middle column of the red room.
|Monsters||BG and BIO||IOD||WMD|
- This is one of the few maps to not include demons or spectres.
- This is one of the brightest levels in the game, despite never seeing the outside.
- This is one of the smallest maps in the game.