Cosmetically modified version of The Bad Place better known as Dm4 - one of the six deathmatch maps included with Quake.
As lava has frozen, this opens up for a new gameplay and meta around the big room floor, and to some degree MH room aswell. There are ways out of the fluff without rocket jumping, but they're not very simple to execute.
Hidden spot below bridge
When passing underneath low bridge, wading through the fluffy snow, you're invisible from above. Have this new spot in mind as you walk the bridge, or get ready for a nasty surprise.