is a structure originally built to be a man-made, closed ecosystem in Oracle, Arizona, USA. It was constructed between 1987 and 1991, and was designed to explore the complex web of interactions within life systems in a structure that included: five areas based on natural biomes, an agricultural area, and human living/working space.
Unfortuantely, in 2007, the entire site was sold to private developers, leaving the buildings open for tours -- but rapidly falling apart. Recently, photographer Noah Sheldon took his camera, and put together a beautiful series of photos documenting the decrepit state of Biosphere 2
. Here's a gallery. Very interesting stuff! Enjoy!