This is a remix of a UT map, brought to us by SLAM, with assistance from Sharpknux as SLAM does not actually have UT on his computer. The full name is apparently "Gateway to the Abyss", a title that certainly fits this screenshot! Hot enough for you?
There are stairways, ramps and lifts to the surface in the four different directions you can see, and all the pick-ups you tend to need. The small surface area looks quite pretty, in fact, except that somebody left a certain heavenly body as a square of default-textured bubbly-concrete, floating high in the sky! The design of the map has been well-tested on UT of course, and I think we can be sure that it all flows well, and that the Bots know exactly how to ruin your evening...
Sharpknux remarked that Abyss looked better than the original, and with SLAM's deft touch with the traditional textures, that does not seem surprising. Some of his original NAB maps ought to be remixed for UT, though including all the NAB textures would make for a hefty download! Just look at that screenshot, and smell the hot metal and sulphur - admit it, you want to get the map, and start to explore it, triple strike in hand, right...?