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.