And also, you stole the idea I was probably never going to get around to do!
The exact same with me
Anyhow this is great, maybe using a custom textures and adding more details like instead of it being blocked of with half blocks you could actually see what is past it by making glass look like chain link fences.
[EDIT]: believe it or not, but every singe room and hallway is included so far including the sewer, it just doesn't look like it.
I also suggest using a texture pack that's TF2ish (if you ever use it in a deathmatch server) and I've also finished a re-skinning of SDK's guns and grapple that makes every weapon a TF2 weapon: viewtopic.php?f=25&t=205920&p=2974033#p2974033