Wind Cave National Park
Wind Cave is one of the best known examples of a breathing cave. The cave is recognized as the densest cave system in the world, with the greatest passage volume per cubic mile. Wind Cave is the sixth longest cave in the world with 168.02 miles (270.40 km) of explored cave passageways (as of 2025) and the third longest cave in the United States, though it is only the second longest cave in Custer County, South Dakota behind Jewel Cave. Despite the close proximity, no connection has ever been found between Wind Cave and Jewel Cave and most geologists believe the caves are not connected. Above ground, the park includes the largest remaining natural mixed grass prairie in the United States, as well as the southern terminus of the South Dakota Centennial Trail (read more).