Buried under layers of limestone and sandstone hundreds of feet thick, Jewel Cave is more ancient than South Dakota's Black Hills, which adorn the landscape above. The cave lay undiscovered until 1900, when two brothers, miners and part-time cowboys, felt a strong wind coming from a small hole in the ground at the base of a cliff. When they enlarged the opening, they found passages filled with the glittering calcite crystals that give the cave its name. Although its discoverers marveled at the cave's natural beauty, few believed the find to be significant. Even after Pres. Theodore Roosevelt proclaimed Jewel Cave a national monument in 1908, the government was unwilling to fund development. Americans then took up motoring, roads improved, and tourists flocked to the once remote Black Hills. In the 1930s, the Civilian Conservation Corps created facilities to accommodate the influx. Yet it was not until an adventurous couple from the East received permission to explore and map the cave that its true importance was realized. They and fellow cavers who accompanied them or followed in their footsteps discovered a massive multilayered labyrinth. Jewel Cave now is the second-longest cave in the world, and the exploration continues.