This map plays much better if you can't see the monster count, a la the first level of the Aliens TC. It's a maze of claustrophobic sewer pipes at right angles. If you navigate by sight, you'll probably bump into a corpse or two, which barely registers until you're right on top of it, giving you quite a stop. One shadowy body in particular is a little creepy. Very good soundtrack.
A short intermission that's got more of Bye's epic architecture without much fighting. A bunch of hitscanners will melt out of the shadows and you might do some pole-dancing with an archvile.