The level was converted with the luxf3d tool and is loaded as l3dlevelmodel, which generates an octree from it and applies the lightmaps.
Authors of the level (textures were removed):
Alcatraz (http://www.planetquake.com/bighouse),
Nunuk ( http://www.planetquake.com/nunuk),
Sock (http://www.planetquake.com/simland)
Use W+A+S+D and your mouse to fly around, SPACE and C to climb or sink.
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