What are the essential structures of a city? « Has Anyone Ever?

populated by virtual people with simplified behaviors. Right now Im just concentrating on the essential structure/parts of a typical city so I can make a simplified,general template as a guide for building this environment. To start, I listed some building block structures ... entertainment(movie theater, shopping mall, sports stadium, park) learning(school, university, library, museum) This list is still growing. I dont need to model complicated, realistic buildings. ...