Red Keycards let you use the Pylons; Red Green Blue; U-Pylon.
Green Keycard Magenta Yellow Cyan D-Pylon
The brave can buy a Red Keycard from Freedom City. Green Keycards are only salvaged.
Once inside, you'll be prompted three times to press one of three buttons. If you know the right combination, you'll be teleported somewhere else, probably to another pylon. This is easiest done with TCode.
Some places can only be reached by pylon.
Fortresses can access the pylon network. Be sure to have the right keycard, or a Warper, on hand for the trip back!
Sometimes typos, 'level' instead of 'zone' and things in the documentation and newsletter give that in the oldest versions of LOD, the wasteland was a multi-level dungeon. The Grim Reaper (Hell) even can have a Rope, which was presumably used for climbing up and down between levels. The other wasteland-adventuring door game, Operation Overkill II, does have a multi-floor wasteland.