Hashima Island aka Battleship Island. Former coal mining facility owned by Mitsubishi Motors, it was once the most densely populated place on earth, packing over 13K people into each square kilometre. Operated from 1887 until 1974, after which the coal industry fell into decline. With their jobs gone and no other reason to stay in this mini urban nightmare, almost overnight the entire population fled back to the mainland, leaving most of their stuff behind to rot.
Hashima Island in the South China Sea as featured in the James Bond film Skyfall. The island was constructed by Mitsubishi as a coal mining facility and was quickly abandoned when the coal was depleted in 1974. Daniel Craig saw pictures of the island while on location in Sweden filming Girl with the Dragon Tattoo and suggested Hashima as a location for the next James Bond picture.