Yeah, Ptolus, Waterdeep, Sharn, Sigil - all of those are urban environments where conceivably the entirety of the campaign can take place in the city.Not commenting on whether there should be a setting because I always do homebrew, but not sure why you think it couldn't be an urban setting. Many of my campaigns are city based. Cuts down on the number of fireballs wizards cast but other than that it works just fine for me. Not sure why you think it wouldn't - I just have a lot of NPCs, factions, mysteries and a city sized dungeon.