Built into the surrounding rock formations is an organ piano, ready to be played by anyone who passes.
Stalacpipe Organ, as it's known, is only part made by a human hand. The instrument's mechanics were made to utilize the natural elements around the organ in order to make sound. The sound comes from 37 stalactites that were worked into the design.
Atlas Obscura calls it the “largest musical instrument in the world,” which if you're counting the cavern around it, isn't hard to believe.
The various organ “pipes” are actually rubber mallets that strike stalactites around the cave, and are scattered around 3.5 acres. The sound fills the entire cavern.
Leland Sprinkle, who incidentally has the best name ever, created the instrument in 1954. It took him three years to complete the organ, and it was completely worth it.