Rushmore Cave, Show cave in South Dakota, US

Rushmore Cave is a show cave in South Dakota measuring 3,652.6 feet (1,113.3 m), the ninth longest cave in the state. Its passages open into named chambers such as the Entrance Room, Post Office, Image Room, Big Room, Fairyland, Rope Room, Geode Room, The Rouge Room (Party Room), Arrowhead Room and Floral Room. The limestone holds boxwork and dripstone formations: stalactites, stalagmites, columns, helictites and flowstone.

The cave was discovered in 1876 by local miners when a broken water system diverted water into a small hillside opening. This accidental discovery led to regular exploration and eventually to opening the site for visitors.

The cave's named chambers, such as the Post Office, Image Room, Fairyland and Floral Room, were coined by early explorers and tour operators; the Post Office room is said to hold carved initials left by those first visitors.

The cave maintains steady temperatures year-round, so bring a light jacket and wear sturdy shoes for walking underground. The guided tour takes about one hour and requires moderate activity level to navigate the passages.

Rushmore Cave is the ninth-longest cave in South Dakota, with a surveyed length of 3,652.6 feet (1,113.3 m). It lies closer to Mount Rushmore National Memorial than any other show cave in the United States.