Isolation

"Isolation" is a map first referenced in the Halo 3 Beta code. It then appeared in a leaked photo of the list of Halo 3 maps. Most recently, IGN made an article describing it. It is a medium sized map, taking place in an enclosed, grassy area. The environment is in a bio-bubble which has contained the flood on the Ark. Two bunkers act as the bases for the teams, with openings in the sides for shooting out of the bases. They connect into a network of underground tunnels. These tunnels offer close-quarter combat. Sentinels can be seen flying above the map and can be shot at and destroyed with a weapon like a sniper rifle or battle rifle.

IGN: There's an interesting thing that happens when you play Isolation for a while, correct?

Tyson Green: There is, but I don't want to spoil it.

"Isolation is a medium sized map, set in an isolated biosphere which has been seeded with the basic Flood organism."

This makes reference that the flood might come out if you play the level for a long time. This is reinforced by clusters of flood biomass in many places around the map. However, it has been observed that in as little as five minutes of gameplay on the map, small Flood organisms appear all over grassy areas of the map. Some people have reported after longer periods the grass in the area of these spores will die and turn black. It is unknown if this is the full extent of the map's changes. It should be noted that the very apex of the map's hill remains clear of Flood forms.

The map does well for CTF and Team Slayer games, and even Infection, as recommended by Tyson Green. It is similar to Midship due to it's symmetry and openness on the top of the map.