Damnation

Damnation is a multiplayer map in Halo: Combat Evolved and one of the few non-symmetrical maps in Halo: Combat Evolved. It incorporates both a high and low flag base, providing heavily vertical gameplay.

Summary
This map was not remade in Halo 2 mainly because it would be less interesting without fall damage. It contains a Flood dripping effect much like those in the campaign and it bears the layout of a Covenant research laboratory. It is highly popular on the Oddball and Team Slayer gametypes.

Although the Bungie.net description claims that it is a Covenant structure used to control water flow into a section of Halo Installation 04, the fact that the Covenant had only two or three days to set it up makes it difficult to reconcile with known facts.

Bungie.net Hints:

 * During CTF events stay close to the flag locations and snipe across the high teleport road and the low dam crossing. Communicate well and the flag is yours, as it is easy to attack the flag bases from multiple sides at once.
 * Use the two Sniper Rifles to surprise and effectively suppress opponents. There's a good hiding place near the uplink crate.
 * Watch your step! There are a lot of areas on Damnation where you can walk off a ledge and die. Pipes, on the other hand, can be fun places to hang out and get the drop on someone.
 * It was thought that to hop to the pit area from the falls bridge area was impossible, though you can do it the other way. This is actually incorrect - a fairly seasoned Halo: CE player can achieve this jump from the middle fall bridge to the pit area that contains the coveted rocket launcher. This is done by simultaneously performing two tasks: 1) walking over the Overshield power-up and 2) bouncing a grenade at the wall so that it blows up directly beneath your feet.  If timed properly, the grenade will propel the player over the ledge as the Overshield is "powering up", therefore causing no damage to the player's health and maintaining the Overshield intact.  Some things to remember: 1) the fuse times of plasma grenades and fragmentation grenades are different (fragmentation grenade will blow up almost immediately when this specific grenade toss is performed, as it is programmed to detonate almost immediately after "settling" on the ground; plasma grenade will take approximately 2 seconds post-settling to detonate); 2) if timed perfectly, you can throw the grenade at the wall as you are running full-speed at the wall while powering-up with the Overshield just as the grenade detonates (again, WHEN you throw the grenade at the wall depends on whether you are using a plasma or fragmentation grenade) - this is most efficient and helps to decrease the chance that you will be killed by an opponent noticing you prepping for the jump; and 3) getting INTO the pit area does not necessarily mean you are going to GET OUT, as this is one of the most highly-contested spots on the map, with constant grenade detonations going on and players monitoring the re-spawn of the Rocket Launcher.

Trivia

 * Although the map is stated to be on Installation 04, there is no Halo in the sky or any sign of the planet Threshold or its moon, Basis, though if you look into the water outside the map, you can still see what looks like the Halo ring reflected on its surface. Bungie either didn't finish the sky or the processing center is not on Halo. The latter sounds more accurate because the Covenant found Halo only a couple of days before its destruction making the construction of this facility unlikely.
 * This is the map in Halo PC that has the most gameplay lag.
 * Some of the pipes drip a green liquid, presumably the same as the liquid that can be seen in levels with the Flood in Halo: Combat Evolved.
 * Just like Boarding Action and Gephyrophobia, a common mod is to allow the player to jump to the bottom of the ledges and live (making them stuck at the bottom of the level).