ONI Alpha Site

ONI Alpha Site is the second campaign level of Halo 3: ODST, and the first one of the "flashback" levels in the game. It is set in the ONI Alpha Base of New Mombasa.

The level opens two hours after the drop, from Dutch's point of view, as he and Mickey set demolition charges to destroy the bridge leading to the complex to prevent the Covenant forces from accessing it. After destroying the bridge, they fall back into the facility.

Trivia

 * The Firefight map Security Zone is based on the level, namely the courtyard inside the wall surrounding the ONI building.
 * During the drop sequence when the player is in a HEV the ONI Alpha Site and its surroundings can be seen, including the bridge that is destroyed 2 hours later in this mission.