One of my favorite places as a kid was Luray Caverns, a cave in the Shenandoah Valley of Virginia, first discovered in 1878. Filled with stalactites (hanging from above), stalagmites (rising from the floor) and other surreal geological phenomena, it is a captivating sight.
The first image below is “The Dream Lake”, which is only two feet deep but due to the reflections creates an illusion of depth. The next image is the Great Stalacpipe Organ which uses 37 stalactites of different sizes and timbre to create the world’s largest musical instrument. The caves are so deep they were used to create what was called the first air-conditioned building in the world, a sanatarium called Limair.
Check out Luray Caverns on Wikipedia