The main characters in Trichoplax live in a giant spaceship. Their ancestors landed it on a planet for emergency repairs… their people have been their since, now living in the defunct shell of the ship.
I come back to give this ship a design every now and again. I am never really happy with the result. Part of the problem is that it is so BIG. In it was basically a space-city that housed several million families. The second requirement I have is that it looks sturdy. It has to be stable enough to set down on a planet without being crushed under its own weight. It usually ends up looking like a blob or a brick.