The first atomic bomb was tested at the Trinity Site in New Mexico on July 16, 1945, and visitors can see Ground Zero where the bomb was placed on a 100-foot steel tower before detonation. Tours of the site also include the McDonald house where the world's first plutonium bomb core was assembled, as well as historical photographs and a replica of the casing used on Fat Man, the bomb that was detonated over Nagasaki, Japan.