About twenty years ago, landscaper Horace Burgess felt a call from God to build the world's largest tree house. I can't say that what he built is the world's largest, but it's definitely impressive. The house is built around half a dozen trees and is about six or seven stories tall. The definition of a "story" is pretty loose here, given the tree house's interesting mix of floors, half-floors, staircases, and ladders. Somewhere in the middle of the tree house you'll find a chapel / basketball court, which is the perfect representation of this quirky, hand-crafted roadside attraction.
Update 5/25/13: The Minister's Tree House was unfortunately closed by local fire safety authorities last August. However, the "Minister" is working to bring the tree house up to code so it can be reopened. Details: http://www.roadsideamerica.com/blog/state-vs-ministers-tree-house/.