Coruscant

Ah, Coruscant. The most populated planet in all of the Galactic republic. Being the ancient seat of power for a republic that has lasted for millenia, this planet has seen a lot of construction. As the planet's population rose, more and more residences needed to be build. Cities grew and merged into metropoles, then those metropoles merged as well, untill the entire planet was covered in 1 planetsize city.

But that was not the end. Further construction still happened, this time upward, with buildings being built on top of each other. By now, Coruscant has multiple levels.

The surface holds the senate building, where all the governments who are part of the republic send their representatives. As well as the jedi grand temple. Largest of all the known jedi temples and where the jedi council resides.

This highest level of Coruscant is the safest, most peaceful, most well off, most expensive place to live. One level lower is a bit cheaper and a bit more dangerous. and so this trend goes the deeper you go. Until on the lowest level, life is cheap, in every meaning of the word.