Ruby Falls is the highest underground waterfall that is open to the public in the United States.  It is located in the limestone layer of Lookout Mountain.  When this area was folded upwards, joints formed throughout the mountain.  As underground water found its way through these joints, the limestone was eroded and various caves were formed, as was Ruby Falls.

Originally, Lookout Mountain Cave was quite an attraction, but when a railroad tunnel has to go through the mountain, the outside access to that cave was blocked.  As a result, Leo Lambert decided to drill an elevator shaft down to the cave.  In the process of drilling, a new cave was found.  When this cave was explored, it was found to have no outside access and a spectacular waterfall.  As a result, it became the new tourist attraction and, though the elevator shaft made it to Lookout Mountain Cave, people wanted to see Ruby Falls.

In addition to the unique waterfall, Ruby Falls has numerous cave formations.  The formation of these speleothems is very slow and averages one cubic inch every one hundred years.  In Ruby Falls Cave, you will find stalagtites, stalagmites, columns, drapes, and flowstone.  These are formed by water rich in calcium carbonate from the dissolving limestone dripping down from the ceiling of the cave.