BLDGblog has published a series of photographs by Noah Sheldon that capture what remains of Biosphere 2, "a semi-derelict bio-architectural experiment in the Arizona desert." Looking at these images, it's hard to believe some 200 million dollars went into this thing. The site was sold to private developers in 2007. It is still open to visitors. More images on Sheldon's website. Official Biosphere 2 website is here.