Doug Chiang discusses the conceptual art developed for the city of Coruscant: Part 2...
George liked both of these directions, so what he wanted to do was combine both stylistic elements into one image, and that's what you see in the third picture. It was like taking Manhattan and scaling it way, way up. All of these buildings are mile- and two-mile-high skyscrapers. We never really see the floor, because this is a city of such large buildings. Each one of them is several blocks wide at the base. This was the overall view, with flying traffic going throughout the city -- a very 3D world.
From here I developed another sketch which is taking the same idea but getting a little more personal. We see a public transportation station, where we have these large, ocean-liner-sized busses docked at a Grand Central Station-type building, and we see people getting on board.