On 16 July 1945 a plutonium bomb nobody had ever fired was set off on a New Mexico tower after a night of storms. Trinity showed that implosion worked, and it shaped what came next at Potsdam, Hiroshima and Nagasaki.
In September 1944 the world's first full-scale plutonium reactor went critical beside the Columbia River, then shut itself down a day later. B Reactor made plutonium for Trinity and Nagasaki, ran on into the Cold War, and now takes visitors on free tours.
On a Pacific island in the Marshall Islands, a concrete dome 115 metres wide covers a crater left by a 1958 US nuclear test, filled with contaminated soil and debris from the whole atoll. It was built by about 4,000 servicemen between 1977 and 1980, it has no floor liner, and the sea is rising around it.
On the steppe of eastern Kazakhstan the Soviet Union fired its first atomic bomb in 1949 and went on to test more than 450 nuclear devices over 40 years, in an area chosen because Lavrentiy Beria called it uninhabited. It was closed in 1991, and a 17-year operation was needed to secure the plutonium left behind.
