Ghet

In the centuries following The Reaping, the city of Ghet (colloquially known as The Sprawl) grew in the only direction it could - up. Bound by magic, buildings pushed skywards on the shoulders of older buildings below, at times connecting to adjacent buildings. A large portion of the megalopolis rises above the clouds. Think Los Angeles of Blade Runner and New York of Fifth Element.
In the times in between times of The Reaping and today, the barrier was altered to make travel and trade was more easily achievable, however over the last two centuries violent magical storms and an increase in violent wasteland denizens has made movement between the few bastions of civilizations nearly impossible. The movement of people and goods is now only accomplished by the daredevils of the Trader's Alliance who risk the dangers of the wasteland for those few that can afford their breathtaking fees, namely the massive organizations and corporations that, overtly or otherwise, control the city machine. Many citizens of Ghet understand that there are other cities outside of Ghet, but know nothing of them...not even their names.
Class follows wealth, and wealth follows elevation. The higher up in Ghet you are, the higher your class. A permanent cloud layer separates Uptown from Downtown, and ground level is known as The Gloom. Below The Gloom...well, there are all sorts of stories about what horrors are found underground.