Isolation

Isolation is a multiplayer map featured in Halo 3 that takes place at a Flood containment facility.

Discovery
Isolation is a map first referenced in the Halo 3 Beta code, and later appeared in a leaked photo of the list of Halo 3 maps. Most recently, IGN made an article describing it as a medium sized map, taking place in an enclosed, grassy area.

Layout
The environment of Isolation is that of a small bio-bubble that has contained the Flood on the Ark. Two bunkers on either side of the map act as the bases for the teams, with multiple entrances and openings for quick and easy access. Divided into above and below ground areas, combat on Isolation is found in small isolated pockets, and heavy fighting tends to move from one area to the next. The upper level is a grassy hilltop with Forerunner architecture woven into the terrain. A Forerunner edifice exists as the crest of the hill, allowing players a full view of the map's upper level. Players may also choose to quickly access the caverns below by dropping down a chute, and traveling through a porta.

Flood-infested caverns exist on the maps lower level, as evidence by the heavy Flood biomass on the caverns walls, ground, and ceiling. The shape of the caverns appears in the rough form of an "I" or vertical "H" shape, where the crosses of the "I" form inclines leading to the maps upper area. Like the chute and porta, players can also drop down from the center of the map (underneath a Forerunner construction by the Sniper Rifle spawn) landing in the middle of the caverns atop a Rocket Launcher. On either side of the truck of the "I," two small openings exist that allow players to shoot or throw grenades into either base. The overall structure of the map is similar to Halo 2's Midship due to it's symmetry and Burial Mounds due to the openness on the top of the map.

The Bases
The two bases on either end of the map are similar in size, structure, and weapon layout. The difference comes to the aesthetic nature of the bases, as one appears more flood-infested than the other, and thus is more browner in color. A Regenerator exists in the main pylon of each base, as well as a Battle Rifle, Spike Grenades, and a Brute Spiker. Each base has multiple points of entry and exit to the upper and lower levels of the map. Three points can be used for entrance as well as exit purposes, but an entry only point exists for players to drop down from the upper level into the bowels of the base. On the upper level of the base player can find a Mongoose for quick transport to the power weapons of the map, as well as Fragmentation Grenades a Brute Shot and a Battle Rifle. When you go to one of the lower levels of a base and look through a window you can easily toss a gernade to the other base.

Upper Level
At first glance, the upper level of the map appears vast but also looming. The bases are separated by a knobby hill with distinct Forerunner structures at each end. At the top of the hill, players can find the Shotgun, though it has been reduced to a single clip for balancing issues. A set of Fragmentation Grenades and a Flare can be found at the top of this structure, with Battle Rifles on either side as well. A chute, segmented by a porta, allows players quick access to the flood-infested caverns below. On the opposite side of the map, in a brown-colored Forerunner structure, players can find a Sniper Rifle, Needler and Spike Grenades.

Additionally, players can find two purple tinted Gravity Lifts on each side of of the hilltop. These lifts provide access from the lower level to the upper level, but players are often caught between crossfire as the are vulnerable while in the air before their descent. Typically the main skirmish in these areas occur around the Shotgun and Sniper spawns. Both areas of the map offer a view to other key areas for players to pick off opponents either with the Sniper or a Battle Rifle. Both areas also offer a quick drop to the lower caverns, but are segmented from each base, forcing players to travel further to reach the bases.

Lower Level
This dark and ominous lower level has been noticeably infested by the flood, as evident of the large amounts of flood biomass, and Flood sacs present on the walls and ceiling. The maps much coveted power weapon, the Rocket Launcher rests in the center of this "I" shaped cavern, and is easily accessed by players dropping down from above. A Ghost can be found on one end of "I's" trunk, directly in front of the porta and chute. Players can also find a Brute Shot and Mauler on opposite ends of the "I's" crosses. Heavy fighting tends to occur between the lower levels of the cavern and the bases, as players spawn in specific areas. A team that can control the Sniper Rifle typically has more jurisdiction over the lower levels due to their line of sight.

Trivia

 * Sentinels can be seen flying above the map and can be shot at and destroyed.
 * The Flood sacs on the walls of the cavern do not contain Flood Infection Forms like those in the Flood Infested High Charity. When popped, they scream, rather than spew Infection Forms.
 * In an interview, IGN asked Tyson Green if "there's an interesting thing that happens when you play Isolation for a while..." in which he responded "There is, but I don't want to spoil it." Many speculated that Flood would eventually spawn in the level. It has since been revealed that Flood pods form in the upper areas of the map and the grass seems to die.
 * There is a ghostly face that can be seen when standing at the ghost (vehicle) spawn and looking upwards.
 * Among many players, Isolation is the most hated map of Halo 3. This could be because of the odd layout of the level and the large number of "noob" weapons, like the Brute Shot and the Needler, or the fact that many players don't want to face flood in multiplayer too.