How to get to the keys and access the exit on Doom II level
The Pit:

Note: To see a map of this level that shows the location of
all keys, click here.  To access a demo (LMP file) or video
that shows how to reach the keys and exit, click here.

You begin the level at the bottom of a deep 4-walled pit
located in the south half of the map.  The following
walkthrough will assume the player starts from this
position.

BLUE KEY
--------
From the level's entry point, grab the blue MegaArmor next
to you, and then run to the metallic lift in the northwest
corner of the pit, and Activate it.  Get on and ride up.
At the top, walk north-northeast as far as you can, to a
cul-de-sac where you'll see a low, wide rectangular lift
in the northeast corner.
On the wall opposite this lift, in the southeast corner,
you'll find a switch.  Activate this switch and a platform
rises up out of the floor a few paces to the right of the
switch.
Turn back to the lift to the north, Activate it and get on.
When it rises, turn to the southwest and Run off the
southwest corner of the lift, and onto the raised-up
platform ahead of you.  (Remember that Run on a PC is
typically enabled by holding down the Shift key.)
Turn southeast and carefully walk to the southeast corner
of this platform.  From here you can step across, past the
wall-corner to your left, to another raised platform to the
southeast.
Walk a few paces southeast, then look at your Automap.  You
should see a diagonal yellow line to the east, near your
location.  Walk across this line, then head back west, back
to the raised platforms where you were a moment ago.
The wall-corner that divided the platforms has risen up,
revealing some black-tiled walls.  Look for a switch
recessed into the east black-tiled wall, and Activate it.
Now walk west a few paces, then northwest along the raised
platform, to another switch you'll see to the north.
Activate this switch, and the wall to your left opens up,
revealing a large room to the west.  The floor of this room
is somewhat lower than your current location.
Look northwest into the room, and you'll see a low brown
platform, across a small gap of open space.  Jump the gap
to land on this platform, and look for a switch on the wall
near you, and Activate it.  (If you missed the brown
platform and landed on the floor, head south, and then look
for a door to your left, in the southeast corner of the
room.  Go through that door, up the stairs to the immediate
left, then walk east and then north around the corner, and
try making the jump again.)
Once you're on the brown platform and have Activated the
switch there, look southwest for the blue key.  It will be
at the top of a lift, which will drop down temporarily
whenever you step on or off of the low brown platform.
Run off the platform and grab the blue key.

YELLOW KEY
----------
When you get the blue key, look for a blue dot on floor
nearby.  Walk across the center of this blinking dot, and
some stairs should emerge from the floor to the northwest
of the dot.
Now get back up onto the brown platform to the northeast of
the blue dot, via some other stairs that should now lead up
to it.
Walk east into the recess where you'll see a door just
beyond a slim blue pillar.  The blue key opens this door.
There's a switch behind the door which, when Activated,
will open the wall a few paces behind you to the west.
Activate the switch, then Run back to where the blue dot
was, and up the stairs, into the now-open northwest wall.
Ahead you'll see a pedestal in the middle of a vaguely
triangular room.
This pedestal has 3 skull switches; one each on its three
widest faces.  Activate the switch on the northeast face,
then head for the door that will open up to the southwest.
Go through that door and you'll see the yellow key in the
distance, across a large, deep pit of green slime.
Jump into the pit and look north for a radiation suit in
the slime, and grab it.
Now head southeast to a tunnel.  Go to the back of the
tunnel and you'll find a switch there.  This switch causes
the floor in the southwest part of the room to drop down
momentarily.
Activate the switch and quickly run back into the slime,
and continue Running southwest, onto to the lowered floor
before it rises again.
Once you're in the southwest section, you can grab the
yellow key.

THE EXIT
--------
When you're at the yellow key's coordinates, note that
following a straight line north from the key leads to a
narrow dead-end chamber.  There is also a another small
chamber to the east of the key.
Go to the north chamber and Activate the switch there.
This re-opens the black door in the distance to the
northeast.  (It closed and locked behind you, when you
orginally entered this area of the map.)
Now head to the other small chamber off to the east of
where the yellow key was.  You'll find another switch here.
When you Activate it, part of the pit-wall to the northwest
will drop down into the slime; so when you Activate the
switch, run northwest into the slime and continue to the
lowered section before it rises up again.
(If you find yourself stuck in the slime, Run southeast to
the tunnel leading out of the slime, Activate the switch at
the back wall, then quickly Run back to where the yellow
key was.)
Once you're in the northwest section, look for a switch on
the right-hand (east-northeast) wall.
Activate this switch, and the pit-wall to the northeast of
the slime will drop down.  Run to get on this lowered
platform before it rises again.
Once in the northeast section, exit through the square
doorway.
Walk back to the low 3-sided pedestal, and head southeast.
Walk up to the wall and Activate it.  The wall will open
up, allowing you to walk southeast, down into the room with
the blue dot on the floor.
Head south, and then look for a door to your left (east).
Go through the door and walk east a few paces, then south,
back to the edge of the square pit where you began the
level.
Look to your left, at the edge of the pit, for the top part
of a metallic lift, which is raised to a height just above
the floor your standing on.  Activate it and it'll drop
down.  Jump down to get on top of this lift.
When it rises, look for a yellow-lined door to the east.
Go through and head southeast to the brink of a shallow
darkened pit.
Note: At Skill levels 3 and up, there will be Spectres
(semi-invisible Demons) in this pit.
The exit door is in the pit, at the southeast corner.

To read about or download a demo of this level, showing how
to access all keys and the exit, click here.