- This level occupies the map slot MAP02. For other maps which occupy this slot, see Category:MAP02.
Progress through the level as normal collecting the blue and red keys along the way. In the NE part of the map is a Wolfenstein area which can be tricky. You go inside and get the yellow key, a door closes behind you and a deadly trap is revealed. There is plenty of ammo to get rid of the monsters. Along the northern end is a huge line of switches, in which 1 is the correct one. Press the wrong switch, Cyberdemons will attack you. In order to prevent this from happening, press the third switch (green arrow) in from the left to escape the room. This is a preview to MAP23: Spaceswitch in which this process is repeated many times.
1. In the Starting Courtyard, head east and to the left of the cage behind the Cacodemon is a secret door which reveals the Rocket Launcher and some Rockets. This secret can only be used once!
2. In the Yellow Key room, once you get the yellow key a heap of switches are revealed. Press the fourth switch from the very right to reveal a BFG9000 and Invulnerability sphere.