Wikipedia
Stratobowl
The Stratobowl is a compact natural depression within the limits of Black Hills National Forest in South Dakota, south-west of Rapid City. In 1934–1935 it housed a stratospheric balloon launch site, initially known as Stratocamp, sponsored by the National Geographic Society and the United States Army Air Corps. In 1956–1959 the site was reused by the U.S Navy Project Strato-Lab.