Oak Ridge National Laboratory Visitor Center, Tennessee

Oak Ridge is a massive government laboratory complex and nuclear material processing plant constructed first during the Manhattan Project. Facilities constructed at the time included the largest building in the world, used to create a "mere" 100 pounds of Uranium 235 for the first few atomic bombs. The Oak Ridge National Laboratory occupies around 10,000 acres of the 35,000 acres comprising the Oak Ridge Reservation, making it the largest science and energy national laboratory in the Department of Energy system by acreage. It has 1,200 buildings.