Aquapolis was a prototype of a floating city created by Japan's Kiyonori Kikutake.
It was exhibited at the Sea Expo 1975 in Okinawa and shipped to Shanghai in 2004.
The Aquapolis was build to present the audience an utopian vision of a future life on the sea. As the Expo was designed to envision "the sea we want to see" and human's future engagement with the sea's ressources, a floating city inidicating the sea as human habitat was a main attraction of the show.
The Aquapolis was floating on the water surface, held only with a structure of ancors. It crossed the seas two times in it's life, once from Hiroshima to Okinawa after it's construction in the 70's and once for it's disintegration in Shanghai in 2004. During exhibition it was a functioning city was a post office and the Japanese government issuing passports.
All images under Wikimedia Commons License.
The Aquapolis is featured in German underwater video pioneer Hans Hass' film "Living under water" from 1976. Footage can be seen from 9:30, however the entire film gives interesting insights into the thinking and prospects of that time.
In German, no subtitles.