Warning: Wikipedia contains spoilers
Coruscant was The Capital of the Old Republic[?], the Galactic Empire, the New Republic[?], and the Yuuzhan Vong occupation at various times.
It was a huge city covering the entire planet. New buildings were built on the old. As a result, there was virtually no exposed land.
The concept of a city covering an entire planet is not entirely new. The planet Trantor in Isaac Asimov's Foundation novels is probably the first fictional planet to be totally urbanized, but it was not the last.
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