It's described as "Tethered to the mountains by a giant chain," a reference to Dr. Robotnik's fortress in the Sonic the Hedgehog game Sonic CD.
This could be a reference to the University of North Carolina in Asheville, 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. 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.