Rat's Nest

Rat's Nest is a Halo 3 multiplayer map released through downloadable content on December 11, 2007.. Rat's Nest is a large indoor vehicles map that resemble an area from the campaign level Crow's Nest, with internal vehicle accessible roads, tight corridors, walkways suspended above areas and vents. In the distance, Pelicans and Hornets pass by. It was used by the UNSC as a weapons, fuel and ammunition storage facility up until the Second Battle of Earth. Above the UNSC facility is the source of Kenya's water supply Mount Kilimanjaro.

On November 19, 2007, Microsoft released information regarding the first Halo 3 Heroic Map Pack. Rat's Nest is one of the maps included in this bundle. The map pack retails for 800 Microsoft Points ($10 USD), and was released on December 11, 2007. However as of March 25th 2008 the Heroic Map Pack is free of charge to all Xbox Live Members.

Description
This map is, essentially, a big figure 8 track (note, a digital 8, meaning vehicles must turn 90 degrees to cross straight from one side to the next). The map is very open and vehicle-based around its perimeter and center, with close combat and medium sized rooms everywhere else. It has two Warthogs and Mongooses parked outside of both bases, and small rooms connecting each base. On the edge of the road, there is a small outdoor road. On the upper road there is a Ghost and Sniper Rifle, below that Active Camo, then a Gravity hammer and a machine gun turret above that, providing a commanding but exposed view, then the Rocket launcher by the cliff. A Pelican is positioned on a landing platform visible from the track, but it is unusable and unaccessible due to death barriers. Pelicans and Hornets fly by in the distance.

Trivia

 * If you listen closely to the big green pipes, you can hear Drones flying and bumping into each other inside the pipes. This is no doubt a reference to Crow's Nest where you first hear Drones passing through the pipes, before breaking out and engaging the player.
 * Bungie stated in an update that the level includes actual rats. There are rats, but they are dead. If they were alive, they may have confused players by showing up as tiny blips on their radar. Strange enough, as they could have been edited to remove the blips like the Sentinals in Isolation.
 * There are Hornets and Pelicans seen flying in the background of the outdoor area. The Hornets can be shot down with a Spartan Laser.
 * Rooster Teeth, the producers of the popular machinima series Red vs. Blue, made their D.I.Y video here and in two other maps.
 * Rats Nests code name was 'John Carpenters Prince of Dorkness'.
 * This level was first announced on the Bungie Weekly Update of October 12 2007.