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. The music for this level is distant crashing metallic sounds along with haunting orchestral music. The level also introduces Cacodemons, Lost Souls and a brand new enemy exclusive to Doom 64: the Nightmare Imp. This level 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).