Known to Native Americans for centuries, Wind Cave was named for the strong air currents that alternately blow in and out of its entrances. The cave’s winds are related to the difference in atmospheric pressure between the cave and the surface. When the atmospheric pressure is higher outside than inside, the air blows in, and vice versa. With more than 150 miles of known passageway divided into three different levels, Wind Cave ranks among the longest in the world. It’s host to an incredibly diverse collection of geologic formations, including more boxwork than any other known cave, plus a series of underground lakes, though they are located in the deepest parts of the cave not seen on any tours. All tours are led by National Park Service rangers and leave from the visitor center. These tours allow you to see the unusual and beautiful formations with names such as popcorn, frostwork, and boxwork. The cave remains a steady 54ºF year-round, so wear closed-toe shoes and bring along a jacket or sweater. Tickets are sold at the visitor center and typically sell out two hours before each tour during summer, so plan accordingly. Check out the park website for the different tours, times, and pricing.