Underwater cities aren't actually that rare. There's Port Royal in Jamaica, submerged when it was hit by an earthquake in 1692. There's the ancient city of Dwarka, India, whose ruins were discovered in 2000. There's Atlantis, the most famous underwater city of all (location tbc).
But now the Shimizu Corporation, a Japanese construction company, is planning a city that will be underwater on purpose, rather than as the result of a natural catastrophe. And, naturally, they've designed it in the shape of a 500m sphere, connected to the ocean floor by a 15km spiral umbilical cord:
The aim is to install residential and business units in the main sphere, then use the base of the spiral as a research centre for scientists who would harness energy from sources on the ocean floor. One helpful side effect of this process would be oxygen, which is nice, as people do so like to breathe. According to Shimizu, the sphere could house up to 5,000 people and would be entirely self-sufficient.
The city would be accessible by the top of the sphere, which would float just above the water level in good weather, but could also sink by up to 2km below the surface.
The scheme sounds a little outlandish (it's not clear, for example, what the 5,000 residents of this "self sufficient" environment would eat). But officials at the company claim the city could be built by 2030, for the low, low price of 3 trillion yen (£16bn).
Hideo Imamura, spokesman for the company, told the Guardian:
“This is a real goal, not a pipe dream. The Astro Boy cartoon character had a mobile phone long before they were actually invented – in the same way, the technology and knowhow we need for this project will become available.”
Take that, ye of little faith.
All images: Shimizu Corporation