Biosphere 2

Biosphere 2 is the largest indoor ecological research center in the world, and from 1991-1994 was the largest, longest-term experiment in Closed Ecological Life Support Systems. It was built near Tucson, Arizona by a company called Space Biospheres Ventures, which was founded by the Synergists, an intentional community based near Santa Fe, New Mexico. After a two-year enclosure from 1991-93, and a six-month closure in 1994, with eight people living inside each time, control of the facility passed to Columbia University, which continued doing ecological research there but did not keep the structure air-sealed. This semi-closed system continues as both a research facility and a tourist attraction under the University of Arizona, which took over in 2007.