Coruscant
Geologically, the planet comprises a molten core with rocky mantle and silicate rock crust. It is larger, and has stronger surface gravity than Earth. However, the ubiquitous repulsorlift technology available on the planet allows many species, including humans, to live there in comfort.
Throughout the thousands of generations of galactic history, the entire surface of Coruscant has been covered over by sprawling skyscrapers and cities. The planet's oceans have all been drained and kept in vast underground caverns for future reuse. The only body of water visible is the Western Sea, a body of water created artificially for tourists and natives alike. There are some portions of the city that are actually under the sea. The Western Sea has many artificially created islands floating on it, used by tourists on holidays. The only other piece of Coruscant's landmass that has been left untouched are the Manarai Mountains, twin peaks that stick up out of the ground near the famous Imperial Palace. Many floating restaurants revolve around the Mountains, giving patrons a unique view of the natural wonders.
Since there are no bodies of water available to feed and water its trillion inhabitants (despite the fact that it rains on Coruscant, as seen in Revenge of the Sith), Coruscant's architects along with many others from around the galaxy worked together to build a self-contained eco-system in the massive buildings set all over the planet. Engineers also developed a complex series of huge pipes through which polar ice is pumped through to the cities of Coruscant. Almost everything on the planet, from clothes to packaging and machinery, is recyclable. Another problem for a world like Coruscant is the unimaginable amounts of carbon dioxide that its trillion being population generates each day, so atmospheric scrubbers were put into place in orbit to remove it. Galactic Standard Time was developed on Coruscant and revolves around the hours Coruscant has in a single day, which is 24 hours, with 368 local days a year.
