|Hiroshima Peace Memorial|
According to Wikipedia:
At 8:15 on August 6, 1945, Little Boy — the first atomic bomb to be used in war — detonated almost directly above the dome (shown the the photo above). The building's vertical columns were able to resist the nearly vertical downward force of the blast, and parts of the concrete and brick outer walls remained intact. The center of the blast was displaced 490 feet (150 m) horizontally and 1,968 feet (600 m) vertically from the dome, having slightly missed the original target, the distinctive "T"-shaped Aioi Bridge. Everyone inside the building was killed instantly.