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Carlsbad Caverns National Park
Vast limestone caverns carved from an ancient reef in New Mexico
Some 750 feet (230 m) below the Chihuahuan Desert lies the Big Room, a single chamber almost 4,000 feet (1,220 m) long and the largest cave chamber in North America. Carlsbad Cavern and more than 119 other caves in the park were not carved by flowing water alone. Sulfuric acid, formed where hydrogen sulfide from deep oil fields met oxygen-rich groundwater, dissolved the limestone of a Permian reef that grew in an inland sea about 265 million years ago. That same reef forms the Guadalupe Mountains, which rise above the park on the Texas border.
President Calvin Coolidge proclaimed Carlsbad Cave National Monument in 1923, and Congress made it a national park on May 14, 1930. It became a World Heritage Site in 1995. Visitors can walk down through the natural entrance or ride an elevator to the Big Room. On summer evenings, hundreds of thousands of Brazilian free-tailed bats spiral out of the entrance to hunt insects, a spectacle rangers narrate from an amphitheater. The park also contains Lechuguilla Cave, among the deepest caves in the country, which is closed to all but research teams.