How to exit PlayStation Doom level 59, Club Doom:

Look for the bar (the low, long "bench") in the southwest
corner of the room.  Go around behind the bar, and turn to
face east.  You should see a skull switch at the east end
of the bar.
On your Automap, the bar will look something like this:

 ____________________
|   _______________  \
`--'               |__|
                 /
           Switch

Activate this switch, and a door will open in the middle of
the east wall of the room.  The door stays open for a few
seconds, then closes.  Run to get through the doorway.
You'll be at one end of a small maze.  Work your way around
to the door in the east wall of the maze.  That door leads
into the exit chamber.