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 in 1903 by President Theodore Roosevelt, it was the seventh national park and the first cave to be designated a national park anywhere in the world. The cave is notable for its calcite formations known as boxwork, as well as its frostwork. Approximately 95 percent of the world’s discovered boxwork 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 one of the longest caves in the world with 149.01 miles (239.81 km) of explored cave passageways, as of 2018. Above ground, the park includes the largest remaining natural mixed-grass prairie in the United States.