The Halo 3 Heroic Map Pack will be released December 11.  The Three maps will be Standoff(Jodrell Bank), Rat's Nest(John Carpenter's Prince of Dorkness), and Foundry(Art Vandelay).

The symmetrical valley of Standoff, with its entrenched bases and fields of boulders is ideal for mid-sized objective and Slayer game types.

The vast, labyrinthine passages of the Rat's Nest bring something completely new to the multiplayer experience: an indoor vehicle paradise. Strongly influenced by the Campaign mode, this map is ideal for big team battles.

Foundry is the ultimate Forge map. Players can edit every single object in this voluminous industrial warehouse, placing stairways, walls, bridges, and tunnels to create an entirely new play space and build almost any kind of map imaginable.

Check the full story at http://www.bungie.net/News/content.aspx?type=topnews&cid=12983