Driving through the Arizona desert on my way to explore Kartchner Caverns, I pictured myself crawling through a dark tunnel, a flashlight in my hands and a rope around my waist. Twenty-five years ago, Kartchner's discoverers, a couple of amateur spelunkers from Tucson, had shimmied through passages so tight that inhaling was a challenge. In 1988, when the state acquired the caverns, it promised an extraordinary level of environmental preservation, even if that meant turning away visitors by the busload. This heaven would wait.

Naturally, I called ahead to find out what to wear. I expected the dress code to include sturdy old clothes, steel-toed hiking boots and head and eye protection.

Try Hawaiian shirts and Reeboks. Kartchner Caverns State Park, which opened to the public Friday, is a geology theme park, and a pretty good one, attached to a cave that anyone can explore.

The first surprise was the 23,000-square-foot Discovery Center, one of the largest nature museums in the Southwest. Inside, fiber optics, holograms and tons of plastic goop used to simulate limestone illustrate the formation of Kartchner, which began with water dripping through the stone 100 million years ago.

From there, Disney-style trams took me to the cave entrance, where a giant metal door set into the hillside looked like the entrance to Space Mountain. Although tours of Kartchner are on foot, the tram might well have driven straight into the cave--which, it turns out, now accommodates wheelchairs.

I was astonished by the amount of work that had gone into leaving the cave alone. The Parks Department had created 3,500 feet of carefully banked walkways. ("It used to take two hours to reach this point," said our guide, Marlo, after we had been walking under five minutes.) In the two football-field-size limestone rooms now open to the public (a larger one is still off-limits), colored lights give the stalactites and stalagmites a Vegas glow. A sound system has been installed for the multimedia show, which is centered on a 58-foot column called Kubla Kahn. Motion detectors ensure that the lights and sounds greet each arriving tour group.

The state expects its $28 million investment to pay off, thanks to admission fees of up to $14. Although not nearly as large as Carlsbad Caverns, 400 miles to the east, Kartchner appears to be more colorful, even without the illumination. Stalactites and stalagmites, shimmering curtains and hollow "soda straws"--including one an incredible 26 feet long--look nearly as authentic as the plastic versions in the visitor center.

It's true that great strides have been made since the days when--according to Marlo--visitors to Carlsbad were handed tiny stalactites as souvenirs. Last year, a construction worker who snapped off a hot-dog-shaped hunk of Kartchner was prosecuted and fined; the stalactite was glued back on. But there's more to preservation than keeping hands in pockets. Kartchner is a living cave: You can still see and hear water dripping through the limestone. To ensure that the process continues, humidity is kept at nearly 99 percent. That's why the big front door leads to an airlock, isolating the cavern from the dry Arizona air. And lighting is kept low, since illumination could cause spores brought in on clothing to sprout inside the cave.

So awed were its discoverers, Randy Tufts and Gary Tenen, that they conspired to keep the cave a secret for years. Among their few early confidants were James and Lois Kartchner, the owners of the land. Eventually they got word to Gov. Bruce Babbitt (who accidentally broke off a stalactite on his first visit). So great was the fear of vandalism that the state legislature was asked to appropriate funds for Kartchner without knowing where it was. But after 10 years of pouring money down a hole, the legislators finally demanded the cave open to visitors this century. Hence the debut this month.

Tenen, now 49, explains the development of Kartchner this way: "When we found it, it was a virgin cave. But it was 10 miles from an interstate on a gentle slope, and someone else would have found it. There would have been graffiti in no time. The only way to protect it was to develop it. If it had been high up in the mountains, at the end of a rigorous hike, we probably would have sealed it up and kept it to ourselves."

Sure, he has misgivings. As for the sound-and-light show, he says, "I expected to hate it. And I did the first few times. But then I went through with a group, and I noticed that all the chattering stopped as soon as the music came up. Suddenly, people were looking at the cave, focusing on it the way Randy and I did 25 years ago. My eyes teared up."

To discover a place is, inevitably, to ruin it. If you really want to experience the drama of negotiating tight spaces, there are always the "crawl-through holes" in the Discovery Center.

Kartchner Caverns State Park is near Benson, Ariz., about 50 miles east of Tucson and nine miles south of Interstate 10. Tours are given daily, except Christmas. Tours are $14 per adult, plus $10 per car. Reservations are strongly recommended (tours, in fact, are sold out through the end of the year). Details: 520-586-2283, www.pr.state.az.us/parkhtml /kartchner.html.