Biosphere 2 is a manmade closed ecological system in Oracle, Arizona. Constructed between 1987 and 1989, it was used to test if and how people could live and work in a closed biosphere. It explored the possible use of closed biospheres in space colonization (Biosphere 1 is planet Earth).
The experiment showed the difficulty of copying the functions of the natural capital of the Earth biosphere with infrastructural capital constructed by humans. Despite expenditure of over $150 million, this attempt at a new biosphere did not sustain eight humans for a prolonged time. Biosphere 2 is currently exploited as a tourist attraction.