Sado Island that has a perimeter of approximately 280 kilometers had once been home to Japan’s most prominent gold mine. Tunnels have since been developed as tourist routes, with the ruins of a vast flotation plant of 35 meters high, 115 meters wide, and 80 meters deep as well as a thickener of 50 meters in diameter, attracting attention and increasing the island’s appeal as a sightseeing location. The integrated landscape of the bold structure covered in greenery, is often likened to the popular animation film “Laputa: Castle in the Sky.” At the same time it also evokes the impression of an Asian ruin.