10. Area 51, USAIt is a remote detachment of Edwards Air Force Base. It is located in the southern portion of Nevada in the western United States, 83 miles (133 km) north-northwest of Las Vegas.
The dirty bomb was detonated in April 1957, spreading the an area of 895 square acres with Plutonium. Some clean-up was attempted, but the area was mostly just fenced off with barbed wire.
The facility was closed in 1973. Though there are no hard evidence of all such events here.