Ocean Spiral is a conceptual underwater city, dreamed up by Japanese firm Shimizu, that makes for an innovative solution to the problem of strained natural resources with the explosion in the global population.
The city takes the form of a massive sphere dubbed the 'Blue Garden'. Floating just below the surface, it will contain 75 floors with spaces for hospitality, residential, commercial and research purposes and will accommodate 4,000 permanent residents and 1,000 visitors.
The sphere is anchored to the ocean via a 4-km spiral that takes care of the functions required for the Ocean Spiral complex to operate. Power is generated by ocean thermal energy conversion, food is produced through deep sea aquaculture and water is purified. The spiral also includes a port for docking submarines.
Shimizu believes the project will cost around $25.5 billion and could be completed in only 15 years.