Japan has a small land area but with its population ever increasing (126 million now, making it the tenth-most populous country) and with that the prices of real estate, the authorities have decided to set up new city structures under the sea to ease the pressure on the country's soil.
Sources in Shimizu Corporation, which has made the ambitious plan, said it might look impossible now but the world one day will emulate it.
How will the new cities grow?
Called Ocean Spirals, the huge structures housing the cities would float on the surface of the ocean and submerge when the weather is bad. Each sphere will be 1,600 feet across and can accommodate 5,000 people. The spheres would be placed at the top of the 2.5 miles deep with a research station on the seabed.
Shimuzu said the first sphere will cost £16.2 billion ($25.5 billion) and it could be done by 2030.