Hashima Island, Japan: The Concrete Battleship That Was a Coal City

Hashima — universally known as Gunkanjima, or “Battleship Island,” because its high seawalls and ranked concrete towers resemble a warship riding at anchor — is a roughly 6.3-hectare (about 16-acre) rock some 15 kilometers off Nagasaki that the Mitsubishi company turned into one of the most concentrated industrial settlements ever built. Coal had been worked on the island in a small way since the early nineteenth century, but it was Mitsubishi’s purchase in 1890 and the sinking of deep undersea shafts that transformed Hashima into a self-contained mining city of high-rise apartment blocks, a school, a hospital, shops, a shrine, and even a rooftop garden, all wedged onto an artificially enlarged outcrop.

At its 1959 peak the island held 5,259 residents on its 6.3 hectares — an overall density on the order of 83,500 people per square kilometer, and far higher still in the residential quarter — among the highest figures ever recorded anywhere on Earth, roughly nine times the contemporary density of Tokyo. The buildings that made this possible were pioneering: Building 30, completed in 1916, is generally cited as Japan’s first large reinforced-concrete apartment block, a typhoon-resistant design later replicated across the island. For decades the operation ran continuously, with coal hauled up from shafts that descended hundreds of meters below the seabed and ferried to the mainland.

Hashima’s existence was bound entirely to a single fuel in a single market. As Japan’s postwar economy shifted decisively from coal to imported petroleum through the 1960s, the island’s high-cost undersea mine became uneconomic. Mitsubishi announced closure in 1974; the mine ceased operation in January, and the last residents departed by April 20, leaving apartments full of furniture, televisions, and personal effects to the salt air. The island stood sealed and empty for thirty-five years.

Hashima’s modern fame is shadowed by its wartime history: from the late 1930s through 1945, Korean laborers and, from 1943, Chinese prisoners were conscripted to work the mine under harsh and often deadly conditions, with deaths variously estimated from roughly 130 to well over a thousand — a history central to disputes that accompanied the island’s 2015 inscription as part of UNESCO’s “Sites of Japan’s Meiji Industrial Revolution.” Tours resumed in 2009, and the crumbling towers — battered by typhoons and corrosion — now stand as one of the world’s most studied monuments to industrial obsolescence.