. "The Citadel was a Forerunner superliminal communicator. Located on the edge of the core of Installation 00, the Citadel was the structure where one could remotely activate all of the Halo Array. It was defended by multiple shield-projecting barrier towers that had to be disengaged before it could be accessed."@en . . . "Citadel (Forerunner)"@en . . . . . . . . . "The Citadel was a Forerunner superliminal communicator. Located on the edge of the core of Installation 00, the Citadel was the structure where one could remotely activate all of the Halo Array. It was defended by multiple shield-projecting barrier towers that had to be disengaged before it could be accessed."@en . .