One of the longest and most complex caves in the world is Wind Cave in South Dakota, the namesake of Wind Cave National Park, where the unusually small and numbered cave openings cause gusts of wind to blow through the cave.

Touring the cave you’ll see a unique geological formation called Boxwork that is uncommon elsewhere in the world: 95% of the world’s discovered boxwork is in Wind Cave.

Atop the caves sits 30-miles of hiking trails through the largest natural mixed-grass prarie in the United States, where elk, bison, coyote, ferrets, cougars, and bobcats roam.