Mark Twain Cave

Mark Twain Cave — originally McDowell's Cave — is a show cave located near Hannibal, Missouri. It was named for author Mark Twain whose real name was Samuel Langhorne Clemens. Clemens lived in Hannibal from 1839 to 1853, age 4 to 17. It is the oldest operating show cave in the state, giving tours continuously since 1886. Along with nearby Cameron Cave, it became a registered National Natural Landmark in 1972, with a citation reading "Exceptionally good examples of the maze type of cavern development." The cave — as "McDougal's Cave" — plays an important role in Twain's 1876 novel The Adventures of Tom Sawyer and was renamed in honor of the author in 1880.

Cave data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).