Level 3 [Toxin Refinery] from the original Ultimate DOOM game by ID Software, recreated in 1-1 scale as accurately as possible. The level is completely automated and functional. My recreation of the level uses Multiverse Portals, Craftbook [Bridge]s and [Gates] and of course MobArena to operate.
Level 3 is even larger and more complex than the first two, with multiple coloured doors, secret areas and even more excitement than before!
And it's almost bug-free. I believe the blue door and the drawbridge over the lava moat have issues occasionally. Might need to stand on the reset pressureplates a bit longer...
Pasting in-game puts the level above your head facing SOUTH, with the level entrace just above your head. On flatlands, a few parts may come very close to touching the ground, but it should be clear.
I claim no ownership over the DOOM level or the game. I just recreated it in minecraft for everyone to use and enjoy :)