I'd prefer one that crashed 1,000 years ago, is partially looted, and is now taken over by something else the party has to fight, but I can't be too picky.
It's an adventure for 8th level characters involving a small floating city of an ancient civilization that crashed. Monsters and such infest it as well as ancient traps. The adventure has a teaser by giving the PCs access to some, not all, things required to make the city fly again. DM would have to invent and add those adventures.
4e Neverwinter Campaign Setting has a section on an old crashed floating city that now looks like a mesa. The buildings that survive are near the center, so they cannot be seen from the ground. No maps alas but you could use any walled city as a start to create your own.
Not for 5e (though it'd be as easy as just grabbing stats from the MM and applying them), but Broodmother Skyfortress has a neat little setting to perhaps use as a crashed flying fortress. It flies in the scenario, but you could totally re-tool it to be downed and crashed, with the enemies on it trying to restart it so they can begin a reign of terror or something. Possibly worth using for the excellent GM advice in it, as well.