Working at an arch/engineering firm really lets me borrow old classics on architecture. Usual books have massing, spatial relations and such, and it really gives an idea of where you are at vs. a 5' grid. Terrain becomes real and more 3D, giving the players a sense of limitation in some respects, but opens new doors in others.
I use greco-roman arch in some cities of culture and splendor, and use gothic for the newer large cities. The a few of the desert cities have a middle eastern feel, while dry grasslands and steppes get adobe.
In short, arch sparks imagination more than anything, IMO. Use it all where you can is my motto, as my homebrew has a little of everything if you travel there to see it.