If you're looking for the map, it is under DM_ (Half life death match), the name of the map is

dm_sdm_final

if you want to single it out, simply go to the map selection menu on the main menu and use the search function in the bottom left.

Some important notes: There is a room that can reward or punish you based on which hallway you go through. Several of them are traps, while a select few lead you to rooms with calming remixed music. The traps on the other hand like to take their time brutally killing you.

The "secret" room to the map has a "reset map" button, but it seems to of lost function.
You can still "capture" the main control point platform in the gigantic library, keep in mind since the reset button is broken that this change may be permanent until you reload the map.

The lake behind you when you spawn is very deadly, and has such a strong gravitational pull that it makes it feel like your characters soul was sucked right out of them, there may be easter eggs down there for anyone with godmode. Also note even if you have 1,000,000,000 HP from overheal, that the lake is STILL very deadly, and at some point will become inescapable for the common player.

There are a lot of interesting areas this map has, and a lot of hidden gems, maybe you'll find something I didn't, but I think this should be enough to go off of, just try not to die: This place is full of traps...