Mombasa Streets

Mombasa Streets is the first campaign level of Halo 3: ODST, and an open-world environment known as "hub world". It is set in the city of New Mombasa.

Summary
Unique as a Halo game level, this level is an open world environment, which contains "beacons", objects left by the Rookie's squad members, which trigger "flashback" levels, explaining previous events. In addition to the beacons, the level will also have additional content, such as Audio Logs.

The city map provided by the Superintendent highlights points of interest, such as the "beacon" objects. The Superintendent will also guide the player into the right direction using the city's plentiful digital signs and billboards.

During the first playthrough, some areas in the city are unaccessible, and the player is forced to play the flashbacks in chronological order. Completing flashbacks unlocks more areas in the city, allowing the player to progress to the next beacon. Once game is completed, the city is fully unlocked for exploration, with also some Mongooses for easier traveling around the city.

Plot
The level starts six hours after the Squad's failed orbital insertion, in the occupied city centre of New Mombasa. Some time after the Rookie wakes up, exits his pod and starts to explore the city, the Superintendent will contact him via a public phone and upload a map of the city to his VISR navigation database.

Trivia

 * This level marks the return of the Brute Plasma Rifle.
 * This level is the only level in Halo 3: ODST which does not unlock an achievement upon beating it on normal or above. This is probably because of the fact that this is a free roaming level.
 * This is the first non-linear open-world level ever in a Halo game, and the largest open environment Bungie has ever created.
 * The level's moody atmosphere, from color palette to lighting and music, is said to be influenced by the Film Noir genre.