Containment

Containment is a Halo 2 multiplayer map. It was added to Halo 2 in the Bonus Map Pack. It is sometimes referred to as the map "That's so big, it won't fit into the Xbox."

Introduction
"Containment" was based off of the Sentinel Wall of the campaign level Sacred Icon. It is a large outdoor symmetrical map that is a "biological airlock" between the Flood-infected zones of Delta Halo and the "clean" zones patrolled by Forerunner sentinels. It is set in a fault between two snowy cliffs, and there are two massive Forerunner fortresses on either side of the map, acting as bases and also the barricades meant to defend against the Flood.

Topography
It is similar to Coagulation, in the sense that it's an open, hilly terrain, as well as being a big Snipers map. On each side is an old Forerunner ruin, acting each as a base. Each base, red and blue, has a large gate (resembling a ramp, and functioning as one until opened). About 300 feet from it, is a panel that opens each. This is used to get a vehicle inside, as you can go around through the caves, or you can jump the ledge without a vehicle. There are two fully functional gate switches and opening gates. There are two Warthogs, two Scorpions, and two Banshees by default spawning. It is ideal for large, system link games or even Xbox Live games, about 6-16 people. Any number less than six players could result in a slow match.

The level may also remind you of the classic multiplayer level from Halo: Combat Evolved, "Sidewinder", being set in the snow and having a blue and red base. However, this map is very different from Sidewinder and is not a Sidewinder remake. It was originally intended to be a remake of the Halo PC map, Timberland. The map has many similarities to Battle Creek in the first area, as each end has a complex base with many levels, and is set in a valley with alternate base entrances and teleporters, though of course on a far larger scale.

Tactics

 * Though there are normally only two sniper spawns (one at each base), stay hidden. Snipers favor this large, concealing landscape. Competent snipers can make quick work of an advancing group, due to the open nature of the level. There is an assortment of cover around (the variety of rocks sticking up; the small indent on the sides of the bases, etc.), but not enough for you to shoot it out with a foe across the course.
 * Watch for the mines. They are incredibly devastating. Keeping this in mind, they can easily be used, as a deterrent from a Warthog- the opportunities for traps are endless.
 * The giant ramps open on each of the bases. This allows the Scorpion tank access to the inside.
 * In CTF, if you are defending, always post a guard on top of the base. This is important, as you do not want anyone jumping down from behind and stealing the flag.
 * Don't underestimate the network of tunnels running throughout the level. A dislike of would-be snipers and rocket users, you can easily avoid the open space by learning to navigate these tunnels. Each base also has an entrance (on two sides) from this tunnel network- don't forget about it.
 * The turrets are usually a bad decision. It's asking to be sniped or rocketed, and there's also a fair chance that a vehicle will kill you.
 * In CTF, get the Active Camouflage and enter from the base's roof. Remember to take out any guards beforehand.

Trivia

 * This map was designed by Steve Cotton, who took Halo PC’s multiplayer map Timberland, then went through changes until the environment had underwent a significant change.
 * There are 7 Energy cores (or "bouncing bogey clusters" as called by a Bungie employee) on the map.
 * If you take a Banshee and fly towards Blue Base and head to the barrier, the Library can be seen in the background.

Easter Eggs

 * If you take a Sniper Rifle and look at the Halo around the level near the sun base (the one with the orange yellow glowing buildings) you will see the face of Chris Carney, one of Bungie's developers, smiling. In the Machinima series "This Spartan Life" one of the players gets an unlock and is trapped playing Halo 2 as the face.
 * On the doors at the back of each base, 2 Marathon symbols can be seen on them.

Glitches

 * At red base if you fly a Banshee at the top of the map, you can hit an invisible wall. But if done at the correct angle, you go straight through the wall to a perfect sniping position. You can also boost a Spectre up the base walls, or, if you can waste a lot of time, jump up the walls slowly at blue base.
 * If the gate is already open and you approach the switch, it still says "Press X to open gate".