Little River Canyon, AL
In northeastern Alabama, the Little River snakes across the top of Lookout Mountain before plummeting into the 12-mile-long Little River Canyon. Bordered by broad-faced cliffs, with large blocks of sandstone jutting from the water, this canyon—at 600 feet, the deepest this side of the Mississippi—is home to a handful of perfect swimming holes. Just downstream from the Alabama Highway 35 bridge, follow the short paved path to the bottom of Little River Falls for an easy-access dunk when water levels are low. (High water means dangerous currents.) Or start at Eberhart Point and hike 0.75 miles to the canyon floor to Hippy Hole, where rope swings dangle from trees and a series of cliffs serve as springboards for daredevils.