Nicknamed due to its resembling a battleship, Gunkanjima is among the 500+ uninhabited islands west of Nagasaki Prefecture. In the late 1800s it a coal mine and city was established on the island. In 1959, its residential area population density was almost 14 people per acre (3460/km²), supposedly the highest population density ever recorded worldwide. It was abandoned when the mine closed in 1974.