MAP17: Processing Area (MAP20 in PSX) is the seventeenth map of TNT: Evilution, designed by Tom Mustaine who also composed "More", the music track used for the map.
It doesn't take much to beat this stage, yet much of its challenge is based on the fact that while the map may not be very big, there are a lot of demons packed into its compact size (especially on higher difficulty levels). Much like the MAP04: Wormhole and also the MAP08 from Doom II, the player does not have to explore the entirety of the stage (where many of the monsters, secrets and additional items are held) in order to beat it, and can in fact grab all the keys and unlock the exit with a minimum of fuss following only a few select routes throughout (as mentioned in the walkthrough, which itself is relatively small in scope).
Enter the building via the door to your left. Take the hallway to your right, go up the left-side stairs into the computer room and grab the yellow key. Leave this area the same way you came in and open the yellow door nearby. Enter this "U"-shaped area and grab the blue key on the small platform in the nukage pool. Leave this area and head west back to where you entered the building and go up one of the two staircases to the north. Enter the blue door and grab the red key, but be prepared for an ambush. Leave this area, head back south down the stairs and head to your right into the western part of the map. The exit is in the south-central wall of this room behind the red skull barriers; open them and hit the switch to exit.
From the start, walk all the way to the opposite end of the grassy area and go through the grey door there. From here, hug the right wall until you reach a slightly different-textured wall. Open it to get to the ledge surrounding the grassy area, at the end of which is a super shotgun.
In the room with the yellow keycard, there are two banks of computers. Pressing use on the shorter one causes a nearby floor to lower, letting you access the adjacent courtyard. There's a tall pillar with a soul sphere atop it in one corner of the courtyard; the longer computer bank in the previous room lowers the pillar. So, to get the secret, use both banks before dropping into the courtyard, then run onto the soul sphere pillar while it's lowered.
After taking care of business in the room behind the blue door, pick up the plasma rifle on the circular blue platform in the center of the room. This opens a door elsewhere. Go back through the blue door, and continue east down the long corridor. Near the end you'll see an open wall on the left; enter it and go down the hallway to reach another secret courtyard area.
Part of the hallway leading to the courtyard in secret #3. Pressing the switch in this yard opens the door directly across from the exit switch, letting you access yet another courtyard, this one containing a BFG.
Before you start hunting, open the door behind you at the start of the level to get a blur sphere.
Not really a secret but easily overlooked; to get the combat armor you need to walk onto the edge of the wall next to the steps and drop down into the fountain, press the base of the fountain and it will lower the armor.
To the west of the blue key room is an inaccessible area used to store monsters for teleportation into the level. If the player uses the noclip cheat and walks into this area, they will find the letters "TOM" and "NIИ" stitched into the walls. "NIИ" refers to Nine Inch Nails, and "TOM" refers to Tom Mustaine, the designer of the level.
The map was initially one of the four maps Mustaine submitted to id Software for inclusion in the Master Levels; the others being System Control (the introduction map of the Evilution campaign), an unreleased map (available on Mustaine's web site) that was rejected due to its' similarity to American McGee's Doom 2 map The Inmost Dens, and finally the accepted map Paradox.