When one is creating a city for roleplaying, one usually has to do it himself. There are some programs out there that are getting better, but none that do the job as far as I’m concerned. Lankhmar, the City of Adventure included city geomorphs that are the best out there right now, and those are available as GIFs and FCW (for Campaign Cartographer). There’s geomorph dice from DungeonMorphs, but they are best for villages, not full-blown cities. The hexagonal city geomorphs made for the Town Guard boardgame looked pretty cool, but are not available for download. You might use them as starting points though. There’s more examples here. So I’m left building my own. I’ll let you know how that goes.
In the meantime, there’s a few great city maps out there. The City State of the Invincible Overlord was a great early campaign. It made me fall in love with city campaigns, and I’ve still got my copy. You can buy it for D20 at Amazon. They also Kickstarted it for Pathfinder this year, so hopefully it will be available soon. The City State of the World Emperor was their follow-up in 1980, and it was nice too, but not nearly as detailed as the original. Another great map was the city of Irilian, which appeared in White Dwarf. A complete map of the city was available in The Best of White Dwarf Scenarios (Volume 3). Finally, there’s a great map of Ankh-Morpork that is huge enough to run a good campaign in.