Well, if it was just the walled in area, then it'd be Constantinople or Byzantion... depends on what time period you're looking at. Istanbul spreads over both sides of the Bospohorus and on the opposite side of the Golden Horn.
One thing that I always challenge myself to do is attempt to try either North America, the Americas together, or the entire world all by hand and with no tools/maps to cheat off of. My best one is from 2 years ago but I don't have it with me. I'll try to have it scanned to me. It's my best, but it's still pretty bad =(
Here's one i did for a cartographersguild challege. You had to map 2 points and a pathway full of danger between the points. Most did cities, but I chose a different approach. My kids came up with the idea, and helped decide the danger points. Notice the zombie in the upper right? (It's a big one - actually produced twice this size).