I like caves, but feel suspicious of touristy tours. They usually leave a bland feeling, too easy, too packaged. Not so with Ruby Falls in Chattanooga, Tennesee!
This cave was discovered in 1928 by Leo Lambert, who was attempting to drill an elevator shaft to a different cave system. The shaft broke into a previously unknown cave, and he found the falls after 17 hours of crawling with an exploration team. The next day he returned with his wife, Ruby, to view the beauty of the falls. The falls were name after her.
The visitors do not have to crawl in cave today, but the visit to this cave is not short - you could be underground for two hours easily. The visit involves walking almost a kilometer through the cave system before you reach the falls deep inside the mountain. The falls are deep, at over 400 meters underground, and the source of the water running from them is still not pinpointed exactly.
A wonderful experience, and recommended for everybody. And, if you get bored, parts of the cave have free WiFi!