This modern and energy-efficient 15,000-square-foot home is built within a sandstone cave in Festus, Missouri. Built by Curt and Deborah Sleeper, the home features modern interiors that blend with the natural unfinished sandstone walls. Thanks to geothermal heating and clever design, there is no need for air conditioning or a furnace to heat/cool the home.

This space was previously used as a concert venue and a roller skating rink! It gained fame by being auctioned off on eBay before becoming a private residence.