Named for the jewel-like Nailhead and Dogtooth Spar crystals which line over 100 miles of passages, Jewel Cave is the third longest cave in the United States.
Jewel Cave was discovered in 1900 and was run as a tourist attraction for many years before being made a national monument in 1934.
Elevators take visitors 234 feet beneath the surface. Scenic tours from May - September.