AncientCity
The surface of this planet suffers from extreme weather conditions. It isn't impossible to survive, but life is difficult on the surface. It's not clear what caused this, but the existence of a massive city structure underground suggests the original civilisation on this planet was forced to escape from the surface to survive. Did they break the sky?
As bad as it is now, was it worse when they built the city? What happened to them? How long did they live underground? Nobody knows the answers to these questions. There are no records of the lost civilisation among the worlds that use this planet to dump their criminals. They all know something terrible happened here though. This is a dead planet; you've been sent here to die.
The first signs you'll see of this city are the massive ventilation shafts you'll find on the surface. Careful not to fall into them. With some rope and ladders, you can use them as an easy access into the city below. You'll also find some caves reach the top levels of the city around -140 below the ground.