A Japanese construction firm has unveiled designs for an underwater city which it says could be built within two decades.
Shimizu Corporation, one of the world’s 20 biggest contractors, said its Ocean Spiral proposal would be home to 5,000 people and draw energy from the seabed.
The city would feature a floating sphere, with a diameter of 500m, just beneath the surface of the sea, which would house business and residential zones.
This would be connected to a 15km-long spiral path that winds down to the ocean floor 3km to 4km below. The path would be linked to energy resources from under the seabed.
Shimizu said the project would take about five years to build, at an estimated cost of £16bn.
The firm believes the technology needed to build the structure and to sustain life below the surface of the ocean will be ready in 15 years’ time.
Shimizu envisages Ocean Spiral being an eco-friendly underwater city sustained by energy brought up from an ‘earth factory’ on the seabed. It said the factory would use micro-organisms to turn carbon dioxide into methane, while power generators located along the ocean spiral would use differences in seawater temperatures to create additional energy, a process known as ocean thermal energy conversion.
Desalinated water produced using hydraulic pressure would be pumped into the floating sphere.
Shimzu said the idea of creating communities under the sea is a response to rising sea levels threatening the survival of island communities.
Among the firm’s other ambitious projects are a lunar base, a hotel in space and floating botanical cities.