I said Kamurocho earlier, and although I'm sticking with that selection, I also wanted to give an honorable mention to Flotsam. I think it's probably my favorite WRPG city of all time. The music, the wildlife, the atmosphere, the greenery, the weather, the lighting, the citizenry, the guards, the docks, the nonhuman district, the outskirts, the forest surrounding it and the caves littering the area; I mean it's all just literally tattooed on my mind. It perfectly encapsulates what an RPG city is supposed to be to me, that is it's supposed to feel alive, memorable, inviting, but somehow also dangerous and exotic.
I think I might have to load up Witcher 2 again for yet another playthrough. Dammit I have to stop talking about Witcher 2.