Half Pipes of Hell
Duo has got a nice, big map here, with various areas indoors and out, and, as seen in this screenshot, some useful curving ramps ("half pipes") if you happen to have your skateboard with you. And he has done a ballblast version too, which comes in the same download pack, along with various texture files - and you may well find you need UTcrypt.utx as well, which Black Ninja also has available from his idrive - or if you have Unreal Tournament on your hard drive, just dive into the UT textures, and copy and paste it across.
So, a good place, it looks like to me; it came out at the same time as a number of other good maps, so it has not been played very much, I think - while the two main map download sites have both been having problems, which has cut its availability. Go to Black Ninja's idrive, and grab it, along with as much else as you have the time for, is the advice.
I like the place; it has so much in it, different levels and corridors and lifts and stuff, things that you may not find the first few times you play. Beautifully thought out and staged, I think. Duo has generally not textured movers, which helps the visitor to know which bits are likely to move, but this is a splendid arena...and with a ballblast version too!