I could see that working.
Simple, straightforward, flexible - I like it!
Too simple, no challenge - I don't like it.
Okay, it's a really simplistic idea, but I'd like to see what some of the more experienced minds here come up with. No restrictions on how the circle or circles are to be used, and the actual circles themselves don't have to be visible on the final map, just evident (like for example, a city whose 'blocks' are actually circular parks surrounded by buildings).