That kind of matches some mental images I have of Ringworld cities. Especially the Library.
Evidently, Niven was envisioning anti-gravity like a permanent magnet. Boy, that would be fun to play with! Magnets are magic too, though.
More discussion and description of the Flying Castle here. Both above and below the referenced post.
I still haven't spotted previous depictions. It may be that they were removed from the server.