National Park Guide: New Mexico's Carlsbad Caverns

— -- Beneath a rugged landscape, a vast system of limestone caves is one of the most prized geologic landmarks in the country.

The caves within New Mexico's Carlsbad Caverns National Park were formed 4 million to 6 million years ago. Paula Bauer, management assistant at the park, says that although over 100 caves have been identified, there's a good chance some have not yet been discovered.

"There are 117 known caves, but we keep finding more," Bauer says. "Call us back in a couple years and there could be more."

Lechuguilla Cave is currently the largest known cave in the park, with over 130 miles of mapped passage and over 1,600 feet deep, Bauer says.

Scientists believe the cave system was created when hydrogen-sulfide-rich waters mixed with rainwater and dissolved the limestone along folds and fractures on its surface, the National Park Service website says. The result is an immense cave network and vibrant ecosystem, welcoming hundreds of thousands of visitors each year.

California native Alex Weisman says he has visited Carlsbad Caverns twice, most recently on a cross-country road trip with his younger brother. "The sheer size of everything, you really feel how big everything is, and it's mind-blowing," Weisman says. "They have the caves lit up, and you can't see just how far it goes."

Carlsbad Caverns also preserves parts of the Chihuahuan Desert, which supports an array of plant and animal species including mammals, birds and reptiles.

During his most recent visit in 2010, Weisman says, he and his brother participated in the Bat Flight Program. Every evening in the summer, Brazilian free-tail bats swarm out from exits in the caverns in search for dinner.

"Thousands upon thousands of bats come out, it's just insane," Weisman says. "It almost blots out the sun."

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About the park

Size: 46,766 acres

Visitors: 365,000 in 2011

Established: 1930

History: Although Carlsbad Caverns' history as a national park is just over 80 years old, scientists believe human use of the caves and its cultural resources began in prehistoric times. Since then, Indian occupations, European exploration and commercial tourism have left their marks on the area.

When visiting: The park is open all year except Dec. 25. The visitor center is located at 727 Carlsbad Cavern Highway, Carlsbad, N.M. Visitor info: 575-785-2232.

Of note: Researchers are currently studying microbes in Lechuguilla Cave, the largest cave in Carlsbad Caverns. They believe the "extremophile" microbes in the protected cave could help generate a possible cure for cancer.