Caves breathe. They inhale and exhale, depending on the vagaries of barometric pressure, and sometimes they give off the warm, fetid smell of bat guano.

It took only a few deep breaths of that telltale scent to lead cave explorers Randy Tufts and Gary Tenen to the discovery of a lifetime—not just an enormous cavern filled with spectacular formations, but that rarity, a "live" cave a million years old and still growing, just below the surface of the southern Arizona desert. Outside, the temperature can be 100 degrees and rising, but in the cave it is a constant 68 with humidity at 99, a sort of subtropical rainforest in the dark, wet and dripping, growing stalactites and stalagmites and a phantasmagoria of preternatural sculptures. The discoverers dubbed it Xanadu; when it opened as a state park last year, it was Kartchner Caverns, named for the family who owned the property.

Tufts and Tenen, then students at the University of Arizona, first wriggled into the pristine cavern in 1974. They mapped miles of passageways and two massive rooms, each the size of an opera house and filled with the kinds of natural treasures, called "speleothems," that set cave lovers' hearts aflutter. Tufts and Tenen understood the fragility of the cave; its balance could easily be disturbed. If the desert air were allowed in, the cave would dry up. They knew that human intrusion would likely sound the cave's death knell and that it was only a matter of time before other spelunkers would come upon it. "Finding that cave was like having a child," Tufts says. "We felt responsible for it. We made a sort of promise to the cave, that it could trust human beings."

What happened next would turn out to be a marvel of cooperative conservation. For 14 years, the cave was kept secret by a coterie determined to preserve it. Along with the two discoverers, it included the Kartchner family, Arizona's then govenor Bruce Babbitt, and Ken Travous, the state's director of parks. Early on, they crawled through the mud to experience the cave firsthand. One of the Kartchner sons, Max, climbed out, covered in mud, to report, "We were in complete disbelief at the size and beauty of it. It was almost a sacred experience, so exquisite and out of this world." When their help was needed, geologists, bat biologists, and cave experts were let in on the secret. Eventually, they concluded paradoxically that the best way to save the cave would be to open it to the public under carefully controlled conditions.

Flying into Tucson, I looked down on a sere desert strewn with shrubs that looked like a network of veins. I tried to remember Samuel Taylor Coleridge's poem and got as far as "In Xanadu did Kubla Khan/A stately pleasure-dome decree:/Where Alph, the sacred river, ran/Through caverns measureless to man . . . " I was about to encounter such a cavern, somewhere beneath that austere Arizona landscape. From the airport I drove east on Interstate 10. Near Benson, I could see in the distance mountains that once sheltered the Chiricahua Apache chiefs Cochise and Geronimo. State Route 90 led to the new Kartchner Caverns State Park, its buildings tucked into the Whetstone Mountains.

The state has spent $28 million on the park, including air locks to allow people into the cave while keeping hot air out, misting to maintain moisture, and a complex monitoring system to check the cave's health. Only 20 people are allowed in at a time, a limit scrupulously observed, to the dismay of those who arrive without reservations.

I wandered through the sprawling Discovery Center, where a replica of the cave allows children to squeeze through small openings and touch formations. One exhibit depicts the colony of myotis bats that returns each summer to use the cave as a nursery for its babies. When my tour was announced, I made my way to the area where Ranger Carla Mullen started out by assuring us that if anyone should even think about reaching out and touching a formation, she would not hesitate to break their arm off. Some in our group giggled. Mullen continued with a litany of do-nots. Thoroughly forewarned, we hopped onto a tram that carried us up to the cave. On foot, we entered through what looked like a heavy steel refrigerator door, waiting until everyone was in before it was shut. A second door opened into the cave, where we found our way along a dim trail. At specific points we would gather. Lights would be turned on to reveal the formations, slick and sparkling—amazing layers of travertine in rich browns and greens, beautiful, whimsical, and wondrous. The names given to different forms sounded like a grocery list: turnip shields, soda straws, cave bacon, carrots, fried eggs. Each had been formed by water dripping, flowing, seeping through Escabrosa limestone, drop by drop, for thousands of years.

In the Throne Room we waited for the lights to come up to play on the cave’s pièce de résistance—a massive column 58 feet tall called Kubla Khan. It looked like some intricate Chinese sculpture that had taken centuries to carve; the lights threw shadows on the walls beyond, a drop of water, or "cave kiss," landed on my arm.

The park's assistant manage, Frances Adrian, had told me, "Different people have different revelations in there. Some walk away with tears in their eyes, some people clap. It truly is one of God's cathedrals." Someone broke the silence to ask how this cave compares to others, like the much larger Carlsbad in New Mexico. "Carlsbad is to Kartchner," Mullen answered, "as Home Depot is to Tiffany's."

I walked out with the ranger assigned to pull up the rear; his job was to keep an eye out for souvenir collectors.

"Surely no one would dare?" I suggested.

"Last week," he told me, pointing to a spot just above our heads, "a woman reached up right there and snapped off a soda straw." These delicate formations grow one-tenth of a millimeter a year, so she had made off with a formation already thousands of years in the making.

People are clearly the gravest threat to the cave. In my hour-long visit, I left behind 160 million dust particles from my clothes, shed 60,000 fragments of skin, 2,000 lint particles, 170 watts of heat, and 25 quarts of carbon dioxide. And so do each of the 183,000 visitors who pass through each year. Parks Director Travous says all of those things have been taken into account, even to replacing the moisture my clothes had absorbed while underground. But other cave experts claim there are already signs that Kartchner is drying out; even Tufts and Tenen worry that the park isn't on top of its data collection. The idea, from the beginning, was to preserve the cave, alive and growing, for generations to come. I asked Adrian, the assistant manager, if she felt that had ever been a realistic goal. She answered with conviction, "The people who work here are passionate about the cave; they will never let it down."

For general information: (520) 586-4100,www.pr.state.az.us; for tour reservations, (520) 586-2283.

Photography courtesy of Kartchner Caverns State Park

This article was first published in January 2001. Some facts may have aged gracelessly. Please call ahead to verify information.