Episode One: Knee-Deep in the Dead You must be on level three to access the secret level in DOOM. First, there is a room with an elevator with armor on it in the northwest corner of the map. Press the red button in this room. This opens a corridor in the room where you can see a glowing sphere. The room it leads to has some lighted alcoves. Walk up the stairs. You should be able to hear a mechanical sound. This is the sound of two alcoves being lowered. The map looks similar to this drawing. (I love the beauty of ASCII art) Walking into this room normally, the alcoves rise before you can see them. But, if you run up the stairs to one of the alcoves fast enough, you can get in it and rise to a secret door. Alcove 2 leads to the blue glowing sphere. Alcove 1 leads to an island surrounded by ooze. You can get a rocket launcher here. In alcove 1, follow the ooze down the tunnel. The tunnel leads to a switch that raises the bridge over the opening ooze pit. A secret door is also near the switch, but the bridge leads to the secret exit. REMEMBER TO HAUL ASS TO THE ALCOVE. :)

Episode Two: The Shores of Hell
When you get to Command Center, walk out the elevator door, and turn right. Walk up the stairs in the far right corner. At their top of the stairs, enter the door to the right. Walk to the end of the hallway. Open the door, and look to the right. Open that door and turn the switch immediately on the right in that room. That switch raises stairs in the hall you just left. Walk up those stairs, get through the red curtain, and get on the transporter. Kill the lost souls in the room you are transported to and open the hidden door there (a lion head marks it). Again use the transporter, and you will find yourself walking towards a marked EXIT-door. Enter and turn the switch.

Episode Three: Inferno
The process of getting to the Inferno secret level is probably one of the most creative things in DOOM, and the most difficult to figure out. The way to get there is from level 6, "Mt. Erebus". You must get inside a blue box with no ceiling which is in a large triangular depressed area with "water" at its bottom. Inside it is a skull switch ending the level. For specifics, the teleporter leading to the ledge above the blue box is located at [0x27ed486,0x2315201]. Getting inside the box counts as one of the secret passage units for the level. Next to the box is a large red building which one can get on top of. To get on top of it, you must use use the secret teleporter in the building with the berserk pack and stairs in it, with the four Imp cages by the entrance. Upon entering the building, you will see a secret opening to the teleporter on the left. The teleporter takes you to a ledge on the top of the red building. If you go to the right along the ledge you will be looking down at the blue box. Unfortunately, the distance is too far to jump. The key is to shoot a rocket at the ledge wall, the explosion of which will throw you into the box. The area on the ledge where you want to fire the rocket at the wall is located at [0x375bead,0xa900072].There is a rocket launcher on the level, on a platform out in the open with a chaingun and a bunch of monsters. Finally the exit inside the blue box itself is located at [0x37f436d,0xc1ffa3c]. You will take a lot of damage in the process, even with lots of armor and health, however, there are a few invulnerability artifacts on the level which will protect you. One is next to the wall where the launcher and chaingun are, and the other is inside a central shack that opens when you enter a nearby enclosure to pick up the green armor.

A HUGE thanks to Paul Falstad for making this section possible.