If you want to see what greenhouses are truly capable of, check out the Eden Project, the largest greenhouse in the world. Located in Cornwall, England, the Eden Project is a sprawling, multi-domed structure that replicates various climates from around the world.
Dubbed a "green theme park," Eden is home to more than 100,000 different plants and hosts at least 1 million visitors annually [source: Icons]. It was established to illustrate humanity's dependence on plants and to stress the importance of sustainable development and environmental research and education.
The facility strives to make as little negative impact on the environment as possible. Virtually all of Eden's water comes from recycled, filtered rainwater, but the site's commitment to sustainability doesn't stop there. In June 2009, plans were revealed for a new geothermal plant that would provide Eden with a virtually endless supply of natural, renewable energy.