Wind Cave National Park

Established by Theodore Roosevelt on 3 January 1903, the sixth national park in the United States and the first cave anywhere in the world to be made one. Roughly 95 per cent of all boxwork formations ever discovered are in this cave, along with frostwork. It is one of the best known breathing caves, and the densest cave system in the world by passage volume per cubic mile, 168 miles of explored passage make it the sixth longest cave anywhere, though only the second longest in its own county, behind Jewel Cave.