Hashima Island, Japan
Formally known as Gunkanjima Island, this tiny piece of land has an incredible history. Believing there was a huge potential for coal deposits beneath the island, the Mitsubishi Company developed it in the early 1900s. Their prediction was correct and Gunkanjima became vital in Japan’s industrial revolution with its increasingly vast submarine coal mine. The mine required workers, so the tiny island built ten story tall buildings. It was known as “Midori nashi Shima”, or the island without green. Korean POWs were allegedly sent to Hashima and forced into slave labor in the mines during WWII. The less than one square kilometer island eventually had 6,000 residents, making it the most densely populated area in the world. The coal ran out in the early 1970s and the island was quickly abandoned. One of the coolest abandoned military bases in the world, the island remains exactly as it was left, although some green things have begun to grow.