With dry land increasingly at a premium, a Japanese construction company has come up with a plan to sink a spiralling city into the depths of our oceans. Each Ocean Spiral will be home to about 5,000 people, according to Shimizu Corp., with each structure also incorporating business and office facilities, hotel and entertainment facilities. A blueprint for the city of the future was unveiled in Tokyo this week, with Shimizu confidently predicting that the first of its underwater cities would be ready for residents to move in as early as 2030. At the surface, the city will have a vast floating dome that could be made watertight and retracted beneath the surface in bad weather. Beneath the dome, the spiral structure would descend as much as 9 miles to the seabed, where an "earth factory" would produce methane from carbon dioxide by using micro-organisms, the company said. The seabed could also be mined for rare earth minerals and metals. Generators would create power by taking advantage of the difference in the temperature of sea water at varying depths, while undersea docking facilities would enable supplies to be delivered and research to be conducted. Shimizu plans to build the Ocean Spiral from resin instead of concrete and to use industrial-scale three-dimensional printers to create the components. via City of the future sinks into the ocean - Telegraph.