Ruby Falls Cave, unlike Lookout Mountain Cave, had no natural openings and could not be entered until the 20th Century. In 1905, the natural entrance to Lookout Mountain Cave had to be closed during the construction of a railway tunnel. Leo Lambert, a local cave enthusiast who knew of Lookout Mountain Cave, decided to reopen it to the public and formed a company to do so. Shortly after drilling started in the fall of 1928, the team discovered a passageway 260 foot underground and still 160 feet above the Lookout Mountain Cave.
Lambert, along with a small crew, entered this opening to explore the new found cave. While exploring they discovered a number of unusual and beautiful rock formations, flowing passages and several stream beds. Pushing their way deeper and deeper into the cave, they finally reached its marvelous jewel, the waterfall. Mr. Lambert and his exploration party were awestruck by it magnificence and beauty, and quickly returned to the surface to share the news. On his next exploration into the cave, Lambert took several people including his wife Ruby to see the many wonders they had discovered. It was then Lambert decided to call the waterfall "Ruby Falls".
Lambert planned to open both the Lookout Mountain Cave and the new found Ruby Falls Cave to the public and offered tours to both caves. Ruby Falls proved to be the most popular with its many unusual formations and of course the waterfall itself. Lack of public enthusiasm finally lead to the closure of the Lookout Mountain Cave in 1935. Development of the Ruby Falls Cave continued.
Electric lights were installed in the cave, making it one of the first caves in the world to be electrified. Later elevators were added to provide hundreds of thousands of visitors easy access to the caves each year.