A Decaying World: Biosphere 2

200 million dollars went into Biosphere 2. The site was sold to private developers in 2007. It is still open to visitors.

The largest sealed environment ever created, constructed at a cost of $200 million, and now falling somewhere between David Gissen's idea of subnature—wherein the slow power of vegetative life is unleashed "as a transgressive animated force against buildings"—and a bioclimatically inspired Dubai, Biosphere 2 even included its own one million-gallon artificial sea. 

A gallery of pictures can be found here.