Halo 3 heroic map pack
From Halopedia, the Halo wiki
This map pack from the Bungie Map Team is nick-named the Heroic Map Pack. It includes 3 new maps including Standoff, Rat's Nest and Foundry. It cost about 800 Microsoft Points ($10) and will be released on December 11th.
STANDOFF
Standoff is a moderate-sized map similar to the Halo 2 Coagulation and Halo:Combat Evolved's Blood Gulch. It is actually an extended form of it, surprisingly has no snipers defaulted to the map and only has 3 Mongooses and a Warthog per base. The bases are symmetrical and are very easily to defend. They have 4 entrances; 1 from either side and 1 from the front and back. Defenders have the advantage at the side 2 and back entrances have to be opened by a remote further inside the base. The rest of the map includes rocks surrounded by large hills and a spartan laser in the centre. There are a few new Forge options to this map as well, like the sandbags and the open crate.
RAT'S NEST
Rat's Nest is a next generation inside-vehicle paradise with a small outside area that is dangerously littered with Gravity Hammers and Brute Shots. There are 2 bases; each base has 3 Mongooses and 2 Warthogs. There is a road that runs around the edge of the map which has a dead end at either side of the map and at each dead end there is a Ghost. Along the road there is also a long tunnel (like the one on High Ground) that is hung above the road by wires. There is also a Pelican landing pad on the small outside area (not usable) that provides a great spot for camping with rockets or snipers. Stretching from base to base, there is finally a pipeline that creates distractions that start up hectic fights.
FOUNDRY
On this map, it is completely Forge-able to your demise. It is the world of endless possibilities. You can forge stairways, tunnels, bridges, landing pads, nearly all weapons, steel plates and thousands more and included also is the weird soccer ball from Halo 2. In Foundry, the maximum for Flamethrower placement is 4. Foundry has endless possibilities and there will definitely be many variants of this map.