Isolation

Isolation is a multiplayer map featured in Halo 3 that takes place at a Flood containment facility. The environment is a small, isolated bio-bubble that has contained the Flood on the Ark. The Milky Way galaxy hangs in the sky. The top level is grassy and untainted, but in the underground caves there is an obvious Flood contamination.

Map Design
Despite its often appearances in Free For All and Team Slayer matches, it was designed for symmetrical objective games. Featuring two symmetrical underground bases, a grassy hilltop above, and the underground caves of flood infected bio-mass.

Topside
Isolation has an ovular shape to it when observed from above. It is a symmetrical map that consists of two levels: above and below. The upper level is a grassy hilltop with Forerunner architecture woven into the terrain. To the north, at the crest of the hill, lies a silver-gray multi-level Forerunner structure. A Battle Rifle spawns at either side of this tower. It can be used either for shelter (underneath, where the Shotgun spawns) or as a sniper perch (by standing on top). Directly behind this sniper perch is an escape chute that provides quick, one-way access to Isolation's bowels through a Porta. From here, the player can go to his left (east), right (west), or move forward (to the south); you (probably) cannot regain entry to the sniper perch by going back up the chute.

Underground
Going left or right will lead to one of the cave's side entrances. At either entrance is a mancannon, which will blast you back to the top of the map. Going south will take you toward the mouth of the cave. Midway through the cave, there is a concrete bunker on either side. The bunkers have portholes for weapons fire. The bunkers can't be entered here. A little further south is where the Rocket Launcher and Ghost spawn. At the southernmost end of the cave, a thin rock ridge extends upward around the map's wall. This makes for another excellent sniper spot. Directly above the mouth of the cave is another Forerunner structure in the shape of an archway, which is rusted-brown. There is another drop-down here, which will put you near the Ghost/Rockets.

Bunkers
On the east and west sides of the map, in front of the two Man Cannons, is a Mauler, and next to that an entrance to each of the respective bases. A Regenerator exists in the main pylon of each base, as well as a Battle Rifle, Spike Grenades, and a Brute Spiker. You can either take a ramp down, or drop in from a hole above. Just above this area is the Brute Shot, a Battle Rifle, Fragmentation Grenades, and a Mongoose.

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.

Trivia

 * Sentinels and Constructors can be seen flying above the map and can be shot at and destroyed, however it is difficult. This is most easily done from the eastern side of the map with the help of scoped weapons.
 * The Flood Growth Pods on the walls of the cavern do not contain Flood Infection Forms like those in the Flood Infested High Charity. When popped, they scream or moan, rather than spew Infection Forms, but they do cause damage to anyone unfortunate enough to stand next to them when they are set off.
 * If you look at the Ark in the distance you can see that the planetoid is missing from the Ark's core.
 * 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 small Flood Pods form in the upper areas of the map and the grass seems to die, though it does take a while for this to occur. But after a while, it goes back to normal.
 * There have been many sightings of the Ghosts of Halo on this map.
 * It is easily possible to stand on the trees after being propelled upwards by the lifts.
 * There is a Porta in the Flood area. It can be accessed from the structure in the middle against the wall, where a player can unexpectedly or purposely drop in, though in a matchmaking update, Bungie has made it harder to get on the ledge in the hole. However, it is still possible to get on the side of the ledge.
 * The textures for Isolation's grass change as time goes by. You can observe this by taking "before and after" snapshots.
 * There is a glitch on this map that allows the player to get behind the Forerunner wall.
 * This is now one of two maps that are Flood based, the other being Cold Storage.
 * Many people use this map to get the Mongoose Mowdown achievement.

Strategies

 * Rushing for the Ghost and Rocket launcher at the beginning. However, also camping beside either of the two and waiting for others to ambush as they attempt to pick them up is also a good tactic if used well.
 * If sniping is your preferred tactic, taking the Sniper Rifle and staying on the outermost edges of the map helps to prevent you from being flanked. A regenerator with Battle Rifle is usually good backup. But make a few kills then move position, people will start hunting you.
 * Entering the lower levels through the "chute" is a good escape tactic. While being chased, strategically throwing grenades toward the exit of the chute can kill or wound any would-be pursuers.
 * In the lower levels, there are the many "spore pods" that explode, with some power, use this to your advantage.
 * Grab the ghost and find people in the lower levels, as this is a tiny area which is hard to escape, so they are trapped while you splatter them.
 * Climbing the trees in this map can provide good ambush points. If you go to the end branches and crouch with a suitable weapon you can sometimes and with practice, occasionally, score easy kills this way because opponents that are not extremely attentive will become disorientated thus easy targets.
 * Holding the structure at the top with a team is extremely effective as you cannot be flanked.
 * A team member stand on top of the structure can spot enemies and call out their position so the whole team can use the high ground to BR head shot them all.
 * Also, if overrun the shotgun spawns below so keep one handy and fall back down the chute and blow all the attackers away.
 * Get the Shotgun, preferably the Battle Rifle and keep a Regenerator to  stay on the open field and you can get some kills using CQB and Long range shots. Use this technique and repeat it again, however go to the shotgun spawn first because it respawns very quickly.

Forge

 * If you place a Portable Gravity Lift at the base of the "chute" you can propel players up the chute instead of down, providing an interesting twist.