Earth (Gaia) is the homeworld of humanity and is currently the de facto capital of the Galatic Commonwealth. Its surface is defined by a vast expanse of nature with pockets of super-dense cities all interconnected with underground vacuum tubes feasible for hypersonic transport. For movement between the most important of locations, the compression of space-time allows for thousands of miles to be covered in a brisk walk, although due to the intensive energy requirements, it is only used sparingly.
Despite the density, no individual is ever lacking in space or privacy. Massive structures extend both into the stratosphere and deep underground, capable of meeting all the living needs of people. In recent centuries, Earth has also become quite cosmopolitan with up to 30 percent of the planet’s demography not human in origin.