Bungie has revealed a new Halo 3 map, called Ghost Town, which will be included in the upcoming map pack. The maps is set in an ancient city, mostly consisting of ruins, as Bungie puts it:

Ghost Town is the fragmented ruins of a small 24th century water purification complex that geographically lies just North and West of the jungle foothills hydroelectric facility from the Sierra 117 mission. The well-protected facility built into a shallow ravine was once home to the Global Water Campaign, where the still somewhat-pure Kilimanjaro meltwater was transported via pipelines from the river and directed to this small outpost where it became further purified, and then transported via GWC trans-African pipelines along the Tsavo Highway for distribution throughout the entire continent.