This natural cave has gone through a variety of transformations. It started out as a mine, then became a worm and mushroom farm, then a roller skating rink, and finally became a family home in 2003. Surprisingly, the 17,000-square-foot home has only one full bath and one half bath but the Sleeper family still loves their cavernous abode. And why shouldn't they? The natural cave climate never goes above or below 70 degrees Fahrenheit and it comes with a built-in groundwater spring pool.