A woman prays along the Motoyasu River in front of the Atomic Bomb Dome at the Peace Memorial Park in memory of the victims of the world's first-ever attack with a nuclear bomb 63 years ago in Hiroshima, Japan. The dropping of the atomic bomb by the US killed an estimated 70,000 people instantly on Aug. 6, 1945, with many thousands more dying later from the effects of radiation. Three days later another atomic bomb was dropped on Nagasaki, ending World War II. It was the last time a nuclear weapon has been used in an attack.