Ruby Falls is not only the deepest underground waterfall in the United States, but it is also the highest waterfall underground.
Ruby Falls is a 145-foot waterfall located inside Lookout Mountain.. The entrance to this underground wonderland looks like a European castle.
Be sure to wear good shoes when you visit. The ground may be naturally slippery in spots.
If you visit during the summer, you might want to bring a light sweater. The temperature inside the cave is around 60 degrees all year long.