Phobos

Phobos is the inner and larger of the two moons of Mars, named for the old Earth god of fear, a son of Ares and Aphrodite. In the era it has been built into something between a city and a machine. Colonization wrapped the little moon, barely twenty-two kilometers across, in added layers of decks and structures extending it kilometers in every direction, and two great docking rings circle it at right angles to one another.

Phobos serves as the primary port of Mars. Cargo craft rise from the planet to its yards, where helium-3 and other exports transfer to the kilometer-long haulers that work the runs between the Core and the Rim. On its surface stands the Hive, a jigsaw city grown by raw economics rather than Gold planning, while within, the hollowed rock holds the Hollows, weightless lattices of cage apartments where the moon's poorest live.