Gunkanjima, meaning “Battleship Island” in Japanese, is an abandoned island off the coast of Nagasaki that boasts the highest recorded population density in the world. This tiny island, at one time filled to the brim with concrete buildings, was coined “battleship island” due to its likeness of a war ship charging through the ocean. What now remains of this desolate ghost town reveals a sad, yet fascinating history.

In the 1890’s, the Japanese corporation Mitsubishi bought a local mining business at a neighboring island called Takoshima. They expanded the mining operation onto Gunkanjima around 1895, sinking two shafts by 1900. What soon followed was a surge in coal mining, requiring an increase of on-site workers to mind the coal. It wasn’t long before a community developed on the island.

By 1917, there were over 3,000 people living on the island the size of a football field, and construction started on the first concrete apartment building. At the time, this was a monumental feat. To put it into perspective–America had built their first large-scale concrete building only 14 years earlier. Construction soon followed for a nine-story apartment complex–the tallest building in all of Japan. Before World War II, Gunkanjima had a total of 30 apartment buildings, when all across Japan there was little building due to wartime efforts. The high demand for coal required that Gunkanjima continue to mine, and subsequently grow.

As the war took young Japanese off to fight, Mitsubishi started to use forced-labor from nearby China and Korea. By 1945, Gunkanjima had practically become a slave labor camp. Close to 1,500 people had died from mining injuries or exhaustion.

In 1959, Gunkanjima had reached a population of 5,259. That equated to 1,391 people per hectare. It is to this day the highest population density ever recorded in the world.

The island sustained itself through a time of prosperity because of the Korean War. Gunkanjima had become a tiny metropolis. There were shops, clubs, restaurants, spas, theaters, schools, gambling halls, and playing grounds. Everything that was needed to live a normal life could be found on the remote island. Its only contact with the outside world was the food that was imported and the coal that was exported.

The growth would not last forever though. In the 1960’s, petroleum replaced coal as the major energy provider. Coal mining was on its way out, and coal mines were closing all around Japan. Finally in 1974, Mitsubishi officially ordered the closure of Gunkanjima’s mines. As quickly as it had been ordered, the island was evacuated. Within four months, the last person stepped off the island. Gunkanjima was now a concrete ghost town, with a shameful history hiding under its rocks.

For the past 32 years, very few people have set foot on the island. In fact, most Japanese people don’t even know about Gunkanjima. Like many sour things in Japan’s history, it has been conveniently hidden from society. The longer it sits unprotected from typhoons and crashing waves, the more the structures crumble–and with them, the history of the silent island.