Hashima (端島), commonly called Gunkanjima (軍艦島; meaning Battleship Island) is one of the most remarkable of a series of hundreds of deserted Japanese islands. Once a thriving coal-mining city its population density grew to be the highest on the planet, packing over 13,000 people into each square kilometer. Workers were crammed vertically in ever-growing buildings and walked daily through ever-narrowing streets.
It operated from 1887 until 1974, after which the coal industry fell into decline and the mines were shut for good. With their jobs gone and no other reason to stay, almost overnight the entire population fled back to the mainland, leaving most of their stuff behind to rot. The island was given a new nickname, ”The Ghost Island.”