This sounds like a great idea. This was the first thing that came to my mind actually when I first heard about lucid dreaming. I would try this but Im not having consistent LDs. After I get my technique right I'll be sure to try this. Also, instead of cites I may just do worlds. I think I would use worlds because it would be easier to have a definite boundary to where it ends, instead of a city that could span forever.

Just my input. Im happy that somebody has brought this up.