The first atom bomb to be used as a weapon, “Little Boy” (as was its codename) was dropped on to the flat terrain of Hiroshima on August 6, 1945. The bomb vapourised buildings and killed nearly 70,000 people directly but by the end of 1945, nearly 100,000 had died from its protracted effects.
https://www.youtube.com/watch?v=t19kvUiHvAE