Just wanted to point out that the fairly-recently released Murder in Baldur's Gate PnP adventure has yet another map of the city. A smallish, though zoomable version is here:
http://www.coroflot....asy-cartography
Note the large area between the city's eastern gate (the Basilisk Gate) and the bridge over the Chionthar river. That stretch was basically all slums (the "outer" city), and featured a neat area called Little Calimshan.
The adventure itself was kind of iffy (I did try running it), but the setting guide that came it for Baldur's Gate is top-notch. It could be a fantastic resource if someone wanted to build a nwn1 or nwn2 module there.
Anyway, as kamal said, build what you think is going to be fun for you! And have fun!