The Lost Sea is the largest non-subglacial underground lake in the United States and the second largest in the world, and you cross it in a glass-bottomed boat.
The cave system around it is Craighead Caverns, between Sweetwater and Madisonville in the foothills of the Great Smokies, named after a former owner, the Cherokee chief Craighead. The Cherokee used the caverns as a meeting place for their councils.
Almost every use the cave has been put to since is a variation on hiding or extracting. Confederate soldiers mined it for saltpetre during the Civil War, gunpowder being in desperately short supply. Moonshiners used the lake area as a hideout, particularly through Prohibition.
The most remarkable find came in 1939, when two cave guides, Jack Kyker and Clarence Hicks, exploring on their own time, came across fossilised bones. They reported them to the owners, who sent them to the American Museum of Natural History in New York. They turned out to belong to a very large Pleistocene jaguar and an elk fawn, and the vertebrate palaeontologist George Gaylord Simpson came down to see the cave for himself.
Beyond the lake the caverns hold an abundance of anthodites, clusters of quill-like crystals that radiate out from a point, along with stalactites, stalagmites and a waterfall.
The tour is guided, takes around an hour and a quarter, and involves a walk down a sloping passage before the boat ride. It stays cool year round, and the boats run continuously, so the lake is the part nobody has to queue long for.
Commons photos · USGS place names · GeoNames · OpenStreetMap
Other places on the map within a couple of hours.
