I think a lot of that may have had to do with rather homogeneous surroundings. There was very little to them. That's not to say High Charity or its later flood incarnation weren't beautiful, but we had already been there. The repetitive locales for missions in Halo CE and 2 kinda made that worse I bet. I think New Mombasa itself could provide a good overall setting. You've got the old city and its run-down architecture, the Uplift and the Reserve, cosmopolitan and newer, "lived-in" centers, industrial areas, and military facilities.