Chimney Rocks Skywalk at McCloud Mountain, along Justin P. Wilson Cumberland Trail State Park (http://www.tnvacation.com/vendors/justin_p_wilson_cumberland_trail_state_park/) in Campbell County. Sounds like you need to make reservations.
Located on the western edge of Lookout Mountain, Cloudland Canyon is one of the most scenic parks in Georgia, offering rugged geology and exceptional hiking. The park straddles a deep gorge cut into the mountain by Sitton Gulch Creek, and elevation differs from 800 to 1,980 feet. Overnight guests can choose from new yurts, cottages near the canyon edge, a modern campground and spacious, walk-in tent sites. Backpackers can enjoy camping in a hemlock grove on the 2-mile Backcountry Loop.
Devilstep Hollow Cave, Cumberland Trail State Park, Tennessee, This beautiful blue water eventually discharges at Head of Sequatchie Spring. We worked all day with the Rangers from the Park and Manuel and I were the last to exit the cave. The pool looked especially nice late in the day.