When I was working on a city ruins, I did an overall large-scale layout of the city, such that it all fit on a large sheet of paper. I marked up anything that was significant at that scale (the palace at teh center, large squares, some large buildings like temples and an amphitheater) and then just drew in the major roads.
I made descriptions of major areas of the city (in this case, due to historical factors the architecture was significant and dramatic), and then did fine-scale drawings of only a few places which I believed the PCs would investigate. Mostly, they did.
I had encounter tables for different regions (day, night, in the parks, near the edge, in regions held by various groups), lots of random tables for exploration of unimportant ruins (ie % ruined, likelihood of finding a minor artifact, likely building use, etc...).
It worked quite well (my players still talk about the city 3-4 years later, so I'm guessing they liked it).