A um.. I don't know, I suck at describing stuff. My best map yet though, hope you enjoy. I recommend you run it on something compatible with doom.exe demos, as stx-Vile made a very nice maxrun.
Espi (for some help and texture wad fixes) Drew "stx-Vile" DeVore (for testing and a demo) NiGHTMARE (for some textures) Gherkin (for Doom Builder) Matt Tagliaferri (for DoomCAD) whoever made the sky texture :P
From scratch of course
Doom Builder 1.1-1.3, Wintex, XWE
Lift near the end can break, minor glitch with horizon