The atomic bombings of the cities of Hiroshima and Nagasaki in Japan were conducted by the United States during the final stages of World War II in 1945. These two events represent the only use of nuclear weapons in war to date.
In the center of Hiroshima, in a part of the city totally destroyed by the explosion and ensuing fires, a long-lost photograph taken shortly after the blast has been discovered among a collection of articles about the bombing.
The picture is a rare glimpse of the bomb's immediate aftermath, showing the distinct two-tiered cloud as it was seen from Kaitaichi, part of present-day Kaita, six miles east of Hiroshima's center. Reprints of the image did appear in a 1988 Japanese-language publication, but the whereabouts of the original were unknown. There are only a couple of other photos in existence (two, possibly three) that capture the cloud from the vantage point of the ground; and, according to the Japanese paper Asahi Shimbun, there is only one other photograph that provides as clear a picture of the separated tiers of the cloud, and that is a photo taken from the Enola Gay as it zipped away. (via The Atlantic)