This amazing ancient cave was kept secret for seven years to protect it from the public.

Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

A labyrinthine underworld of tunnels and caverns hides beneath the city.

This angular brutalist playground turns playtime into modern art time.

The caldera of this mini-volcano has been turned into a naturally heated mud bath.

Bubbling up from deep underground is the warm crystal clear water that fills the Warm Springs Pools, America's oldest spa.

This roadside attraction in the woods of Mississippi is a scalable replica of the Holy Lands during biblical times.

The highest point in Tennessee, Clingmans Dome bears witness to the ravages of one type of insect.

This funicular railway rumbles along for a mile up the nearly vertical face of Chattanooga’s Lookout Mountain.