Tuckaleechee Caverns, Natural limestone cave system in Townsend, Tennessee, US.

Tuckaleechee Caverns is a limestone cave in Townsend, Tennessee, entered beneath the Great Smoky Mountains. Its show cave holds the "Big Room", a chamber that could almost fit a football field, with stalagmites up to 24 feet (7.3 m) tall and flowstone hundreds of feet long. A 210-foot (64 m) two-tier waterfall, Silver Falls, drops through the cave, and the water originates at White Oak Sinks in the national park.

Cherokee people used the caverns in the 17th and 18th centuries; sawmill employees in the area rediscovered them in the mid-19th century. Earl McCampbell opened them for tours in 1931, but the business closed after a year during the Great Depression. Townsend locals Bill Vananda and Harry Myers reopened them in 1953, first guiding visitors by kerosene lamp until electricity was wired in 1955.

The name Tuckaleechee is pronounced TUCK-ə-LEE-chee. Cherokee people used the caverns in the 17th and 18th centuries before sawmill employees rediscovered them in the mid-19th century. Tours began in 1931 under Earl McCampbell, and Townsend locals Bill Vananda and Harry Myers reopened the site in 1953, first leading visitors by kerosene lamp until electricity reached the passages in 1955.

The caverns are accessible only through guided tours offered throughout the year at varying times of day. Bring a light jacket since the interior is cool, and wear sturdy shoes because the underground paths are uneven.

The cave houses SeismicTKL, described in the sources as the most sensitive seismograph system on Earth, monitored by the US Department of Defense and the US Geological Survey. Station AS107 was installed by the Tennessee Valley Authority to measure how dam-building affected local plate tectonics, and during the Cuban Missile Crisis the military noticed it tracked global tectonic movement precisely. It now runs 24/7, transmitting by satellite to the Pentagon, Geneva and Vienna with a precision of 1/300th of a millisecond.