Serious Sam Revolution - Military Decay 2 (Serious) 

Here's a a three-levels campaign set in some kind of military buildings in the middle of nowhere. This second level is set entirely in a military complex with some cool fights and generally reminded me of the first Half Life, especially in the last part. Thanks to the creator Unwary_Thief and to Mydlak for republishing it and adding some stuff
Steam's workshop page:
steamcommunity...
I've played this map in blind run at Serious difficulty. When you see the fades, it generally means that I've died there, or that I went back somewhere to pick up some stuff or that I've reloaded 'cause I let myself be hit too much in stupid ways