Foundry

From MLGWiki

Foundry was released as part of the Heroic Map Pack.

Foundry is a sandbox map meaning you can remove everything. This is good as it means you can totally change the map to how you want it.

MLG has used this to create Onslaught and Amp. Which both of these maps are going to be used in the MLG Pro Circuit and the halo 3 MLG Playlist.