The Halo 3 Heroic Map Pack has gone up on Xbox Live Marketplace, offering three brand new battlegrounds for 800 Microsoft Points (GBP 6.80 / EUR 9.30).
The pack, unveiled last month, will be made available for free in spring 2008 ahead of another map pack's release.
The three maps included are Standoff, Rat's Nest and Foundry - a symmetrical valley map, an "indoor vehicular paradise" and "the ultimate Forge map" respectively, in Microsoft's view.
As reported yesterday, Halo 3 players will be able to download an update to introduce new playlists for the maps from today.
Bungie has also said that the new maps will not interfere with the game for people who do not download them - although the new maps can be included in playlists, they will be excluded if one player in the group does not have them.
For more on the maps, check out our Halo 3 screenshot gallery.