An article in Wired talks about Bungie's attention to detail when doing multiplayer and campaign level design:

Some of the details in Halo 3 verge on the obsessive. While creating several environments based on the area of Africa surrounding Mount Kilimanjaro, Bungie designers used a satellite map of the region to make sure the geography would remain consistent from scene to scene -- and that as the "day" inside the single-player story wore on, the sun would set at a realistic pace. (Even the road signs in the game are "mostly close to real life," a designer told me: When you see a ruined highway sign saying "New Mombasa: 47 miles," that's roughly the distance to Mombasa, Kenya.)

I hope Bungie doesn't get in trouble for admitting that the multiplayer level Epitaph is based on a French cathedral; games that depict shootings inside religious buildings have been taking a few knocks lately. Hopefully the sci-fi renovation will prevent that.