I don't know, most of it, I guess?

A sentient race of flying angel-like(as in they look vaguely similar to how angels are depicted in our western world, they aren't divine within the fictional world) who mostly live on large rocks in the planets ring they chained together with magical chains they happened to scavenge that were once forged by some gods to imprison another god. They don't know where the chains originally came from and they're trying to learn how to make more because their only city is getting pretty crowded.

Aforementioned chained up God was eventually murdered by other aforementioned Gods and fell to the planet leaving not only a giant crater, but also super fertile soil in what is otherwise a harsh tundra largely devoid of nutrients as he partially burnt to dust while falling through the atmosphere. The crater that was created after what was left of him hit the ground resulted in an "eternal flame" that's fed with a natural gas reservoir that was given path to the surface by the results of his fall. Some super lucky refugees found the "eternal flame" and were creative enough to make pipes and use it as a source of steam heat for their homes and to make this now mysteriously fertile soil warm enough to farm. It eventually turned into a city. It's a pretty big city, and if there's an accident, nefarious plot, or the "eternal flame" is otherwise ever put out before the natural gas reservoir is depleted, they're all going to die by natural gas poisoning unless they get out fast enough.

The largest city both by population and "land size" in the world is the last remaining refuge of the once great Lacerti Empire. The Lacerti are one ethnicity of lizard people race and the only ancestral city they have left is referred to by the rest of the world as "The Hanging City". It's often considered the greatest wonder of the world. It's composed of multiple dozens of dense town centers that are built around and between the trunks of trees in a densely wooded swamp. These town centers are connected by bridges. Some of these bridges are made from planks and ropes twisted from vines and others are living bridges that need pruning that are made by carefully training the limbs of swamp trees to form bridges over are large amount of time. The Hanging City started as a small settlement, but as the Lacerti Empire fell and it's inhabitants retreated into dangerous, the city grew to accommodate them.

To actually explain this as realistic, I just can't do it.

The world started as one I used for TTRPGS, so the rule of cool mostly ruled. As long as it kept my players exploring, realistic didn't matter.

Now, I've started writing fiction it. I've been able to make the setting mostly internal consistent, so realistic still doesn't matter.