I don't think this topic has been done before (forgive me if it has). A thread to mention, discuss, describe etc the most evil maps ever.
I begin by nominating "Inferno" and "Thy Flesh Consumed" from the Ultimate Doom. I think those episodes have set a standard with some of the most gruesome and disturbing stuff, which has rarely been reached since. All the moving intestines on the walls, floors of skulls, crucified bodies draining into pools of blood, fire, pentagrams and demons - good stuff.