Virginia's Luray Caves are a mix between a geological feature, an organ, and an electric guitar. In Luray Caves, there is the body of an organ set against a far wall. It looks more like a piano, as it's missing one of the defining parts of a pipe organ: the pipes. Instead, this organ has "stalacpipes."

Stalactites hang down all over the Luray's large central cavern. In 1956, Leland W. Sprinkle, whose name should peg him as an instructor at Hogwarts, converted these geological features into extensions of the central instrument. When the organ is played, each key sends a signal to a rubber mallet, which taps lightly on the appropriate stalactite, which vibrates.

To create music, Sprinkle had to tap stalactites acres from the central organ, but at the bottom of each stalactite is a magnetic pickup. They mimic the vibrations and send them along to an amplifier in the cave. Put together, the Luray Caves are the largest musical instrument in the world. Virginians of means occasionally rent the caves for weddings, because sometimes you're so happy to get married that the very earth needs to tremble at your nuptials.

The Luray Caves have been played by such American greats as Mister Rogers, and here's the giant cavern's rendition of "Silent Night." Enjoy.

[Via Luray Caverns]