343 has outlined a number of new features coming to Halo: The Master Chief Collection.
Chief among them is a new map for Halo 3 called Icebox, which is a remake of the classic Halo 2 map, Turf.
Icebox was originally a multiplayer map from the cancelled Halo Online (343 has added Halo Online maps to Halo 3 before). Unlike the original, which is set in Mombasa, Icebox is set in the Russian city of Tyumen.