While I was heading down I-10 from Phoenix to Tuscon I saw a billboard advertising "Biosphere2." I remembered from a while back about the project, and decided to go see it, even though it was probably at least a day out of the way for me.
The original bioshpere2 project was a study in closed environments. They originally had 8 people sealed in the dome for 2 years, studying the environment and conducting experiments. The next group only lasted a couple of months before they closed it down. The problem was that most of the time was spent gathering food, rather than conducting experiments.
The end result is that the biosphere2 project was opened up, and used as a giant ecosystem laboratory. They also have turned it into a giant tourism place, with tours going out every 20 minutes or so into the biosphere, showing off the old exhibits as well as the current research. It was pretty interesting to see the entire building as one giant greenhouse, as well as the efforts that went into controlling the ecosystem and creation of the weather.
See the pictures here: