Floating cities are possible.
Buckminster fuller was the man
"Well Bucky was later challenged by a wealthy Japanese patron named Matsutaro Shoriki to design a community that could float on Tokyo Bay. Shoriki wanted a solution for Japan’s crowding and imagined boats joined together to make a floating city, not too dissimilar from the Freedom Ship currently under development. Bucky responded to Shoriki’s challenge with the Spherical Tensegrity Atmospheric Research Station (STARS), also called “Cloud Nines.” Though never constructed, these massive, buoyant, geodesic spheres would be filled with hot air and float over the Earth.
I know it sounds like science-fiction, but here’s how Bucky proposed a Cloud Nine would work. A half mile (0.8 kilometer) diameter geodesic sphere would weigh only one-thousandth of the weight of the air inside of it. If the internal air were heated by either solar energy or even just the average human activity inside, it would only take a 1 degree shift in Fahrenheit over the external temperature to make the sphere float. Since the internal air would get denser when it cooled, Bucky imagined using polyethylene curtains to slow the rate that air entered the sphere. He wanted to build Cloud Nines and anchor them to mountains, or let them drift so their inhabitants could see the world. One of the more practical uses he proposed for them was as disaster sites for emergencies."