The discovery of Luray Caverns was equal parts luck and persistence. Cave Hill had long been known locally for its sinkholes and oval hollows -- karst features formed as acidic groundwater dissolved the underlying limestone over millions of years. Others had noticed the pits. Campbell noticed the air. That cool, steady draft meant open space below, and open space in limestone country meant caves. The four men who descended on that August day found themselves in a passage that opened into chamber after chamber of formations: columns where stalactites and stalagmites had fused over millennia, translucent draperies of flowstone, and pools of water so still they created perfect mirror reflections of the ceiling above. They had stumbled onto one of the most spectacular show caves in North America, hidden beneath unremarkable Virginia farmland.

The caverns sit in the Shenandoah Valley at the western foot of the Blue Ridge, carved from Ordovician limestone laid down roughly 450 million years ago when this part of Virginia was a shallow tropical sea. Water did the rest, dissolving passageways along fractures in the rock and then decorating them with mineral deposits carried in solution. The results read like an inventory of geological formations: Dream Lake, where a thin sheet of water creates an illusion of bottomless depth; the Saracen's Tent, a massive drapery formation; and the Fried Eggs, a pair of rounded calcite deposits that look exactly like their name. The entire visitor path stretches over a mile through chambers held at a constant 64 degrees Fahrenheit, a temperature so reliable that Theodore Clay Northcott, who purchased the cavern property in 1905, later sank a shaft into one of the chambers and used the cave air to cool his home -- what he billed as the first air-conditioned house in the United States.

Luray's most famous resident is not a formation but an instrument. The Great Stalacpipe Organ, designed by Pentagon mathematician Leland W. Sprinkle and completed in 1957, uses solenoid-activated rubber mallets to strike thirty-seven stalactites tuned to produce musical notes. The stalactites are spread across 3.5 acres of the cavern, and Guinness World Records recognizes it as the world's largest instrument. Sprinkle spent three years testing and shaving individual formations to achieve precise pitches, then wired each one to a custom organ-style console. The sound fills the entire cave system, reverberating through limestone corridors that serve as the world's oldest concert hall. Visitors encounter the organ as part of the standard tour, its tones drifting through the damp air like something between a church organ and a gamelan.

On the surface, the caverns have grown into a complex that reflects more than a century of tourism. The National Park Service designated Luray Caverns a National Natural Landmark in 1974. The grounds now include a hedge maze built from 1,500 dark American arborvitae, the Car and Carriage Caravan Museum with its collection of over 140 pieces of early transportation history including a Conestoga wagon and an 1892 Mercedes-Benz, and the Shenandoah Heritage Village preserving rustic nineteenth-century Valley buildings. The Luray Valley Museum holds regional artifacts including a 1536 Zurich Bible. The Graves family, descendants of Northcott, still owns and operates the property. Below, the formations continue their imperceptibly slow growth, each drop of mineral-laden water adding another fraction of a millimeter to structures that were already ancient when the first humans arrived in the Shenandoah Valley.