Wind Cave is distinctive for its calcite fin formations called box work and needle-like growths called frostwork. The cave, which was discovered by a sound like that 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.[62] and ponderosa pine forests home to cougars and elk.

 - Wikipedia