, commonly called , is a tiny abandoned island off Nagasaki, lying about from the centre of the city. It is one of 505 uninhabited islands in Nagasaki Prefecture. The island's most notable features are its abandoned concrete buildings, undisturbed except by nature, and the surrounding seawall. While the island is a symbol of the rapid industrialization of Japan, it is also a reminder of Japanese war crimes as a site of forced labour prior to and during World War II. The island was known for its undersea coal mines, established in 1887, which operated during the industrialisation of Japan. The island reached a peak population of 5,259 in 1959. In 1974, with the coal reserves nearing depletion, the mine was closed and all of the residents departed soon after, leaving the island effectively abandoned for the following three decades. Interest in the island re-emerged in the 2000s on account of its undisturbed historic ruins, and it gradually became a tourist attraction. Certain collapsed exterior walls have since been restored, and travel to Hashima was reopened to tourists on April 22, 2009. Increasing interest in the island resulted in an initiative for its protection as a site of industrial heritage. The coal mine of the island was formally approved as a UNESCO World Heritage Site in July 2015, as part of Japan's Sites of Japan's Meiji Industrial Revolution: Iron and Steel, Shipbuilding and Coal Mining. Etymology Battleship Island is an English translation of the Japanese nickname for Hashima Island, Gunkanjima (gunkan meaning warship, Jima being the rendaku form of Shima, meaning island). The island's nickname came from its resemblance from a distance to the Japanese battleship Tosa. History Coal was first discovered on the island around 1810, and the island was continuously inhabited from 1887 to 1974 as a seabed coal mining facility. Mitsubishi Goshi Kaisha bought the island in 1890 and began extracting coal from undersea mines, while seawalls and land reclamation (which tripled the size of the island) were constructed. Four main mine-shafts (reaching up to a kilometre deep) were built, with one actually connecting it to a neighbouring island. Between 1891 and 1974, around 15.7 million tons of coal were excavated in mines with temperatures of 30 °C and 95% humidity. In 1916, the company built Japan's first large reinforced concrete building (a 7-floor miner's apartment block), to accommodate their burgeoning ranks of workers. Concrete was specifically