Cairo Station Vacation

The Cairo Station Vacation is a glitch that can be performed on the Campaign level Cairo Station in Halo 2. This glitch is an exploit in a hole in an overlook in the invisible walls made by Bungie. Bungie never expected anybody to come up to that area, so they didn't put an invisible wall there.

Tutorial

 * Play through the level on any difficulty until you get to the part where you get to the airlock and Miranda Keyes says, "Thanks Chief. I owe you one."
 * Kill the 2 Ranger Elites that come in for you
 * Go outside, and crouch jump onto the first slanted pillar you see
 * Walk all the way up it, and then turn right
 * Walk forward until on the right, you see the second ledge extending out
 * Walk as far as you can on that beam, and when you hit the invisible wall, jump off onto the UNSC In Amber Clad
 * You are now out of the map

What you can do

 * Once outside, you can walk around all over the In Amber Clad
 * Walk all over the map
 * Some of the windows you can somewhat fall through, and you can see part of the map you went through
 * You can walk down to the next area of the map, but since the area hasn't loaded yet, the doors aren't there, the enemies aren't there, and you can't advance in the level unless you go into the area you're supposed to by going back into the map
 * If you're skilled at jumping, you can walk all the way to the back of the In Amber Clad, and jump into the reactors, but you will be stuck once you get in them

Tri-Gate
Outside this level is a Tri-Gate. There are two ways to see it. After you get out of the map, walk up the In Amber Clad, and go towards the rest of the map. Turn to the right once you get to the area where you could see the unloaded next part of the level. Keep following that until you see two paths. One should lead down, and one should lead straight. If you want to see the best view of the Tri-Gate, keep going straight. Unless you can just go right and jump down to the ledges below. Walk all the way to the end and you will see it. If you chose to go the other way, just go farther and then drop down. You should see it better now. Once you drop down from the smaller ledge, you will not be able to get back into the map.