Biosphere 2 / Oracle, Arizona
Biosphere 2 is a 3.15-acre structure originally built to be an encapsulated, man-made, closed ecological system. At a size comparable to two and a half football fields, it was the largest fully-enclosed system ever created. The sealed nature of the structure allowed scientists to monitor the ever-changing chemistry of the air, water and soil contained within - and the impacts that human life have upon the ecosystem - and vice versa. The first mission lasted two years - the second a mere seven months. The site has recently been sold to a land developer but University of Arizona has made an eleventh hour rescue - for the short term.