Wind Cave NP

Established 1/9/1903 Size 28,295.03 acres (114.5 km2) Wind Cave is distinctive for its calcite fin formations called boxwork and needle-like growths called frostwork. The cave, which was discovered by the sound of wind coming from a hole in the ground, is the world's densest cave system. Above ground is a mixed-grass prairie with animals such as bison, black-footed ferrets, and prairie dogs,[61] and Ponderosa pine forests home to cougars and elk.
Wind Cave National Park is an American national park located 10 miles (16 km) north of the town of Hot Springs in western South Dakota. Established on January 3, 1903[3] by President Theodore Roosevelt, it was the sixth national park in the U.S. and the first cave to be designated a national park anywhere in the world. The cave is notable for its calcite formations known as box work, as well as its frostwork.[5] Approximately 95 percent of the world's discovered box work formations are found in Wind 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 seventh longest cave in the world with 154.2 miles (248.16 km) of explored cave passageways (as of 2021) and the third longest cave in the United States.[6] Above ground, the park includes the largest remaining natural mixed grass prairie in the United States.