A subway connecting Grand Storium and The Civilization, as well as running between the Genre-Districts.
Runs Under The Kidney Stones.
If the subway stops between Grand Storium and The Civilization, do not get off. It is a trap.
While river travel is an option, it is far to treacherous to transport large amounts of goods/people between cities. The Hypogeous Highway was created to solve the transport problem without having to cross The Kidney Stones.