I was born and raised in Lisbon, Portugal. It is a city build upon, surrounded by, and influenced by, a river, the Tagus. It is almost inconceivable to anyone to imagine one without the other. From it came food, cargo, people, and, on a couple of occasions, invading armies.
I decided to base New Hades around a river, or rather, four: The Cerebus, The Styx, The Phobos and The Deimos. In my mind, the first two flow from North to South, merge briefly and split into the The Phobos and The Deimos.
I thought that it would be interesting to keep things rooted in the past. There is a lot of material that will be coming from orbit and other planets, but most materials that are not made in the city, will be coming in by cargo ship. Normal, bog standard (maybe droid or drone driven) float-y ships.
So The Docklands and The Factory District will be a hub of activity, 24/7, moving cargo around as fast as it comes in. There are also a number of smaller docks across the river in Rattown, where smaller, darker ships can be found. They might have come from Rust or further afield. What they are carrying or what they are there to collect is a mystery....