Largest closed-ecology vivarium ever

The largest closed-ecology vivarium ever constructed is the Biosphere 2 facility in Oracle, Arizona, USA, with a total sealed capacity of 7.2 million cubic feet (203,881 cubic metres) and an area of 3.14 acres (1.27 hectares). Built between 1987 and 1991, the airtight steel-and-glass research facility, comprising a number of greenhouse structures with some 6,500 windows, was designed to house miniature versions of five different natural biomes on Earth: a 0.5-acre (0.2-hectare) tropical rainforest, a 1-million-gallon (3.8-million-litre) tank recreating the ocean with a coral reef, mangrove wetland, savannah and fog desert.

Biosphere 2 was originally designed by Space Biospheres Ventures to investigate the viability of human survival on another planet by seeing how eight scientists coped being sealed in the habitat complex, alongside some 3,000 species of plants and animals, for a period of two years. In reality, it only operated as a fully closed-ecology experiment for a limited period after an injury necessitated one of the scientists to leave for treatment after only two weeks. More pressingly, by the end of the first year, a dangerously high build-up of carbon dioxide and reduction in oxygen inside the facility, in conjunction with poor crop growth, which the "biospherians" were relying on for food, forced the experiment to be shut down early.

Since 2011, Biosphere 2 has been used by the University of Arizona for climate research.