Perdition's Anteroom by Evan H. Bynum [1.x]
This is a somewhat large level, so named for
its central room with the large spiral
staircase, replete with divers* weapons and
sundry monsters. All secret doors have slight
texture offsets, and there's a computer map
behind one of them. I included every weapon
at least once, and you'll find each kind of
monster save the Cyberdemon and Spiderdemon
somewhere in the level.