Battleship Island （Gunkanjima）, officially known as Hashima, is an uninhabited island located in Nagasaki Prefecture that once flourished as a coal mine. It was nicknamed ``Gunkanjima'' because of its unique warship-like shape.

From the end of the 19th century to the mid-20th century, it rapidly developed as a center of the coal industry, and at its peak, more than 5,000 people lived on this small island. The entire island was covered with high-rise apartment buildings, schools, hospitals, and shopping streets, and it became a symbol of Japan's urbanization at the time. However, with the energy transition, the mine was closed and the island became uninhabited in 1974.

Today, only decaying buildings remain, and the landscape is also known as the "Island of Ruins." In 2015, it was registered as a UNESCO World Heritage Site as a site of Japan's Meiji Industrial Revolution, and has become a popular tourist destination. Gunkanjima's historical value and unique scenery continue to fascinate many people.