The Runit Dome, also called “Cactus Dome” or locally “The Tomb”, is a 115 m (377 ft) diameter, 46 cm (18 in) thick dome of concrete at sea level, encapsulating an estimated 73,000 m3 (95,000 cu yd) of radioactive debris, including some plutonium-239. The debris stems from nuclear tests conducted in the Enewetak Atoll by the United States between 1946 and 1958.