Citadel

Citadel is an upcoming Halo 3 map that will be included in the Mythic Map Pack. No specific release date has been confirmed yet, however this map is expected to be released with Assembly, Sandbox, Orbital, Longshore, and Heretic in the Mythic Map Pack"...in early 2009. “Winter,” as they say." - Lukems in the 10/10/08 weekly update.

Trivia

 * This map contains one of the hidden skulls. Locating the skull earns the player the 'Citadel Skull' achievement.
 * This map is rumored to be a Forerunner map because of the Forerunner symbol on the Citadel Skull achievement.
 * This map could be based on the end of the level The Covenant as where Truth, attempts to activate the Halos because it's called "The Citadel", but may be a re-modeled "Citadel" instead.
 * It is possible this map will not ship with the Mythic Map Pack.
 * This may also be another map similar to Construct, but due to the Shotgun Spree achievement, it may be more of a close-quarters map.