Hashima (Gunkanjima) A former coal mine in the middle of the sea.Lying nine miles from mainland Nagasaki , Hashima—or Gunkanjima (Battleship Island) as it is more commonly known—is the most famous of Nagasaki's 505 uninhabited islands. Given the nickname for its battleship-like silhouette, the eerie island and its former coal mine are one of Japan's most unlikely tourist attractions.