I'm gonna go out on a limb here and say Freiburg from AEG for their 7th Sea game. Freiburg is a box set. It comes with a Player's Guide to the City (full or errors and ommissions to add to the fun, as it is supposed to be a book sponsored by the shops listed therein as a tour guide for PCs to buy), A DM's Guide, An Adventure Book, a Player's Map of the City and a DM's Map of the City. Every building is detailed as to who owns it, how much it costs to rent or buy, what and who's inside and doing what, etc. $34.95 and worth every penny. The most detailed and gorgeous city in years, with a heavy Germanic feel to it. Very nice. The 7th Sea stats will need to be converted to d20, of course, and in some cases, this will be impossible to translate, but its nothing that a good DM can't fix. You really don't need stats for most NPCs, anyway.
Geanavue has a gorgeous dual-sided city/undercity map, rumorquest adventure hook cards to handout, and an amazing level of detail. The problem I had with it was it was so LG/LN bland, safe and boring. I was bored reading it and had to struggle to finish it without nodding off. If you like that kind of "safe" place, then Geanavue is for you. I personally prefer more of a Lankhmar or Zhentil Keep hive of scum and villainy, or a more moderate approach like Freiburg. The good thing about Geanavue is you can start out with a nice, safe place, then mess it up when your villains tear through it or take over. A problem I have with it is it is very Kingdoms of Kalamar-ish, with lots of hard to pronounce, silly sounding names. Another problem is the sleazy port of Loona is not given the amount of detail it needs to be usable. Kenzer wants us to pay for a Loona supplement later this year, which leaves a bad taste in my mouth, as that was the most interesting place in Geanavue.