Buckminster Fuller had some interesting visionary proposals. Here is one for a floating city, AKA Cloud Nine:
From Cabinet Magazine:
1958 Buckminster Fuller proposes the Cloud Nine project, a levitating city of tensegrity spheres, each a mile in diameter. Because the surface-to-volume ratio of such spheres would be vanishingly small, Fuller calculated that if trapped solar energy raised their internal temperature by a mere one degree, they would be able to float like balloons.
http://www.cabinetmagazine.org/issues/27/foer.php
(The full article is on giant spheres - definitely worth a read)
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