
Dismals Canyon is a maze of meandering canyons, huge boulders, caves, and grottoes, all bisected by the flowing waters of Dismals Branch Creek. The area was designated as a National Natural Landmark by the National Park Service in 1975. How the canyon got its name is uncertain. The early Scots-Irish settlers may have named the canyon after a similarly rugged region in Scotland known as "Dismals." A second theory suggests that the settlers named it thus simply for its dark labyrinths and gloomy passages.
The canyon's topography results from eons of geological events during the Paleozoic Era, when the area was a vast swampland. Over successive millennia, the landscape gradually was carved by moving water into a web of canyons and gorges; numerous earthquakes littered the canyon with gigantic boulders as the Earth was reshaped by tectonic events within the Cumberland Plateau. Natural attractions of the canyon include Temple Cave; Rainbow Falls and Secret Falls, two large waterfalls that tumble over large boulders; Witches Canyon; the Champion Tree, the largest eastern hemlock in the world at 138 feet and believed to be 350 years old; and Pulpit Rock, which provides a panoramic vista of the canyon.

The canyon's ruggedness helped preserve it when logging firms moved into the area. Early loggers were unable to profitably harvest the huge trees, with the result being that large numbers of old-growth trees remain, including huge beech, hemlock, and tulip poplar. The forest shelters a biologically diverse understory that includes huge glades of ferns and mosses that blanket the scattered boulders on the canyon floor. More than 350 species of plants and 27 species of trees have been identified in the canyon. The primeval appearance of the park led the Discovery Channel to use the park in several scenes in the show When Dinosaurs Roamed America.

The canyon is owned by Dismals Canyon LLC, which was incorporated in 1995. Facilities at Dismals Canyon include a visitor's center from which interpretive guided tours are offered, a 1.5-mile hiking trail, two rustic rental cabins, primitive campsites, a country store, and a bathhouse and restroom. There is a natural swimming hole on Dismals Creek. A seasonal staff of between two and six people operates the canyon. The canyon is closed from December through February and is open on select days depending on the season.