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.