The ruins of Gunkanjima. (Atlas Obscura/Jordy Meow)

There's no reason you would have heard of Gunkanjima, a tiny, barren island off the coast of Nagasaki. But Atlas Obscura has some incredible photos today about the ghost town it says was once the world's most densely populated place, and it has kindly agreed to share a few with us. (The set, and the story behind them, are worth seeing in full.)

Gunkanjima (also called Hasima or Battleship Island) was once a factory town developed by Mitsubishi to get at undersea coal deposits. At its height in the 1940s and '50s, some 5,200 people reportedly lived there in a space about the size of 12 football fields. As the years went on, however, the mine became less productive -- and in 1970, Mitsubishi closed shop there. The inhabitants left only their 10-story concrete tenements behind.


(Atlas Obscura)

(Atlas Obscura)

(Atlas Obscura)

 

Even by today's standards, those buildings packed a lot of people. According to the latest Demographia report on world urban areas, Dhaka, Bangladesh, fits nearly 45,000 people per square kilometer. Gunkanjima, with roughly 5,000 people in one-fifteenth of a kilometer, would beat that by a lot -- as well as Mumbai, Hong Kong, Bogota and Karachi, some of the modern world's other super-dense cities.

And according to Gunkanjima Concierge, one of the companies that has sprung up to offer private tours of the island since it reopened to visitors in 2009, that's only one of the island's claims to fame: Gunkanjima is also the site, they say, of Japan's first concrete apartment and first roof garden.