Coruscant

Coruscant is a Core World planet that served as the capital to many major Galactic Governments such as the Old Republic, Galactic Empire, and New Republic.

Geography
Coruscant was originally a water planet.

The planet, over millennia, became one giant urban sprawl, engulfing the entire planet in a singular city.

Jedi Temple
The Jedi Temple was located on Coruscant for over 3000 years during the Old Republic.

Siege of Coruscant
The pinnacle of the Clone Wars was the Separatist siege on Coruscant where they attempted to abduct Supreme Chancellor Palpatine (a plot which was actually devised by Palpatine himself who was in control of both sides).