I think may be it is better if we do the city scenery by making boxes, shapes/cylinders for those buildings whithout paying much on the detail. Then come back later for more detail. So, the project can be done at a considerable amount of buildings. If you get bored, the whole city in less detail is still usable rather that scattered detailed buildings here and there.
I'm starting a project for a more detailed Phoenix City scenery, and this is a slightly different story: downtown is on the approach path to KPHX, so having more detail would be good.