Dark grottoes and bats more your speed? Head to the Tennessee-Alabama-Georgia border—The tri-state area of northwest Georgia, better known as TAG (Tennessee-Alabama-Georgia) is literally riddled with caves and underground caverns, making it one of the most spectacular spelunking areas in the entire nation. Watch as the daylight above you disappears, and feel the cold seep into your bones as you descend deep into an unknown gorge. Nearby, you can hear the underground river carving its way through the limestone while it deposits new minerals on age-old stalagmites.

Start with sites located around Johnson's Crook, Pigeon Mountain, and Fox Mountain, and make sure you contact the area's local chapter of cave explorers (The Dogwood City Grotto, www.dcg-nss.org) for updated cave openings and closings.