It's described as "Tethered to the mountains by a giant chain," a reference to the Little Planet in the Sonic the Hedgehog game Sonic CD.
This could be a reference to the University of North Carolina at Asheville, in Asheville, NC, which is in the "Land of the Sky." In terms of video game reference, it could be based on the Little/Miracle Planet, an appearing/disappearing world chained to another one in Sonic CD; It could also be based on Mt. Woe in Chrono Trigger, a floating mass of rock similarly grounded to a mountain by a gigantic chain. Bryan Lee O'Malley's wife, Hope Larson, grew up in Asheville, though she did not attend UNCA. The two of them lived in Asheville for a few years during the production of the Scott Pilgrim series. The building is also somewhat reminiscent of Dark Heaven Castle from the PS2 game Dark Cloud, though the latter simply floats, rather than being chained to anything.