I write ViewingDale which is a zoom browser. The idea there is to map the whole city very coarse and then you zoom into specific areas which you can then optionally map at a larger scale. In this way you do as much of the map in large scale as you need or can be bothered with. A kind of progressive refinement procedure instead of a uniformly high level of detail which involves an appropriately high amount of work to make. Clips of it on youtube should show you the idea.