Warship Island, also known as "Battleship Island", is one of the anime-only places visited in the Warship Island Arc. The island, which is in the shape of a battleship, is where the Sennenryu, a thought-to-be extinct race of dragons that live for 1000 years, come to die and be reborn.
The island may have been based on Japanese reality, as there two places in Japan nicknamed "Gunkanjima", or "Battleship Island". Hashima Island got its nickname from its apparent resemblance to a battleship, which caused the US Navy torpedoed it during World War Two . Mitsukejima also got its nickname because of its shape.