In the deathmatch Installation XJ5, you can get outside to the pit. Grab the rocket launcher and jump down, then turn left. Note the archway above. Blast a hole in the wall below the doorway and start building a tunnel straight to the open window. Just going to the archway above and blasting around the window does not work due to an invisible wall. Once you make the tunnel all the way through, you can look down into the pit below, If you drop down, you will always die. Turn to the left or right and blast a hole big enough to jump into (make the hole on the outside of the wall). Jump into the hole, then make another hole directly in front of you but down slightly. Now that you have made another hole, jump into it. Make sure the hole is not too far down, or you will die from the fall. Repeat this process until you have reached the bottom of the pit. Note: It is next to impossible to get back up once you are down there.