Citadel

Citadel is an upcoming Halo 3 map that will be shipped in Fall 2009 with Halo 3: ODST.

Skull
This map has a skull for the multiplayer achievements. When found it unlocks the achievement, Citadel Skull. It has an image on the skull that resembles a Forerunner glyph, indicating that it takes place on a Forerunner terrain or, given the Covenant's use of Forerunner glyphs, that it is Covenant in aesthetics.

MLG's Take
Citadel: I played this map with Lars. This map was LARGELY inspired by the level "The Covenant" when you were inside of the Forerunner structures, right after the battle with the Hunters who were below the elevator platform. When you have to go around and up an angled jump to battle a few brutes and buggers to get to the platform, that part is almost exactly in the map! It was really cool and was a good close quarters map. Two overshields spawn, and there is a central location with a small structure in the middle with Rockets on top. There are a lot of things hidden in here, very cool map.

Trivia

 * This map is likely be based on the end of the level The Covenant as where Truth, attempted to activate the Halos because it's called "The Citadel", but may be a re-modeled "Citadel" instead.
 * 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.
 * Another theory is that this map takes place inside a Covenant Citadel on the Ark. A Covenant Citadel is also the main base for the Covenant in Halo Wars.
 * Another theory is that this map may be a duplicate or remake of Warlock (Which was a remake of Wizard from Halo:CE) because of its circular shape though this thought is highly unlikely.
 * If a player gets a Shotgun Spree he or she will unlock the 'Pull' achievement.