The World’s Biggest Tree House, located in Crossville, Tennessee. Designed by Minister Horace Burgess, the structure relies on six oak trees as the base to support all five stories, which collectively stand 97-feet-high. Inside, there are more than 80 rooms, including a sanctuary, which can also be used as a small basketball court, as well as a church and bell tower. This year, the building finally made it into the Guinness Book of World Record.