HELP: planned cities...

I have to write a research paper in a few days for my history of architecture class, my topic being planned cities. The professors emphasized asking "research questions" and answering them in the paper. I feel stuck. I can talk about some planned cities - their physical characteristics, history - but don't know what other content to include. So, I am asking for advice... Any ideas? What sort of content should be in my paper? What kind of questions should I ask and answer? Thanks a bunch!!!>