It is the level that starts in the small circular room with blinking lights. In this level there are 3 destroyable cameras, long corridors where appears lots of blue guards from teleporters, and, as I already said, a big room with 2 columns, 2 burning barrels, a planisphere on the left, a big sort of black eye, 2 small useless rooms. You access this big room going down the stairs and going left.
............__..................___
...........I I.................I...I
...........I I____.............I_I.I
...........I____..I____..........I.I
................I.:....I.........I.I
................I.:_.._I.........I.I
................I.I.IOI______....I.I
................I.I.I........I...I.I
.......__...____I.I_I____..._I___I.I
..____I_ I_I..._________...._______I
..I.............I......_I..I_
..I.............I.....I......I
..E...bigroom...P.....I......I
..I.............I.....I______I
..I____..___..._I
.....I___I..I.I
.............X
The map looks like this one (yes, I am mad): O is the starting rooms, E the "eye", P the planisphere, X the blocked passage.
Yes, change-weapon works: press L or R while pressing SELECT.