story identification - Multi-level city high enough off the ground to have atmospheric controls

I'm looking for a book that I read in the late 70s/early 80s. All I can remember is that it took place on a planet where the main city consisted of several levels and that they were so high off the ground that they had sophisticated atmospheric controls. I also think the protagonist was a female, maybe a thief? Sorry this is so vague on the details, but I can't stop thinking about this novel.