There are some amazing caverns in the United States, but Carlsbad Caverns in southeastern New Mexico usually tops the list.
It is an underground wonderland of some of the most interesting shapes of rock formations you will ever see.
And during the summer, it has several hundred thousand bats that pour out in a black cloud beginning at sunset so they can hunt around the Chihuahuan Desert and nearby mountains for yummy moths.
We stopped by in June during a 6,400-mile road trip to Minnesota via Olympia, Wa., Rapid City, S.D., Bentonville, Ark. (headquarters for Wal-Mart) and Dallas, Texas. The only thing that compared in glory was the dressing room for the Dallas Cowboys Cheerleaders, but that's another story.
I had been to Carlsbad -- a two-day drive from Bakersfield -- when I was about 9 years old, and whatever I thought then (55 years ago) did not compare to how magnificent I thought the caverns were on this trip.
I've actually been to a half-dozen caverns -- Lake Shasta Caverns, Crystal Cave and Lava Beds National Monument in California, Lehman Caves in eastern Nevada and Oregon Caves National Monument -- but they are all blown away by the incredible diversity of formations in Carlsbad.
Though not the largest caverns in the country -- Mammoth Cave in south-central Kentucky extends 285 miles and Jewel Cave near Rapid City, S.D. has 160 miles of passageways -- Carlsbad contains 30 miles of underground caves and tunnels that boast some of the grandest views and delicate formations of any.
Carlsbad is called the "Grand Canyon with a roof on it" and it is one of the deepest ever found. Its deepest chamber is 1,027 feet below the surface. The public can view about 14 acres of chambers.
The limestone caves date back 250 to 280 million years ago in a fossil reef -- known as Capitan Reef -- created by an inland sea. The formations were carved when sulfuric acid dissolved the surrounding limestone.
You can walk down into the caves or you can do what we did -- take a 750-foot descent by elevator. Those who walk in go 1.25 miles to get to the same place, but they go the way the initial explorers did.
Though Indians inhabited the desert floor going back to 1400, James Larkin White is credited with being one of the first people to enter the caves in 1898. At that point he was a 16-year-old Texas-born cowhand, so he was just a kid playing in the Guadalupe Mountains.
Over the next 25 years, White became an expert explorer and guide into the caves, which were photographed by Ray V. Davis, whose work was published in 1923 in the New York Times to generate interest. That same year it became a national monument and in 1930 it was designated as a national park.
But White didn't stumble onto a cave. What he first noticed was a huge cloud of bats. That attracted him to the entrance to the bat cave. He went in alone and was astounded at what he saw, according to a 33-page book titled, "Jim White's Own Story." And what a story it was.
The cowboys he told either didn't believe him or refused to come with him to explore. Eventually, a 15-year-old Mexican boy, known only as "The Kid," agreed to go with him on a three-day adventure that included the discovery of a human skeleton and an injury, suffered after White's back was set on fire with lantern oil.
He survived that adventure, but had little luck persuading anyone to pursue making the caverns an attraction. He even met one man who had been to the Mammoth Cave in Kentucky, but nothing came of that.
It wasn't until 1901 -- three years after his discovery -- that his constant talk about the caves and bats finally reached someone who really cared. But the man didn't care about the caves -- he was interested in the bat guano, which was marketable out west as a great fertilizer.
That led to White working as a foreman for a guano recovery operation for 20 years. The bat refuse was packed in bags and buckets and hoisted to the top. Seems that millions of bats over the years can create a healthy supply of the stuff.
During that time, White knew that no one would visit the caves unless there was a path and handrail system. So he set about doing that himself. It took some effort but he finally convinced a photographer to take some pictures of the place. The photographer's only complaint was he didn't bring enough film.
But the publicity led to a survey of the caves and interest by National Geographic magazine as well as the federal government. In establishing a national monument and later a national park, the government pocketed the admission fees; White was just elated that his discovery brought tourists in droves.
Today's visitors to the cool caves -- always 56 degrees -- have handrails, lights, ranger guides, informational radios and plaques, wheelchair-friendly paths and an elevator to enhance their experience.
We got there shortly before the 5:30 p.m. cutoff for visitors to enter. We had to hurry a bit to get past a point where we could see the entire 1.25-mile walk around The Big Room. Those with more time can explore other parts of the caverns on their own or with a guide.
But The Big Room was a treasure of evolutionary shapes created over millions of years. Sulfuric acid, resulting from a combination of forces in the area, went to work as the mountains lifted and the water table dropped. It is known as sulfuric acid dissolution.
As that happened in the past few million years, surface erosion and breakage at the top created the natural entrance to Carlsbad Cavern, sending airflow into the mix. Rain and snowmelt soaked through the limestone rock, dripping and evaporating into the caves below.
Wherever that water drop evaporates and releases carbon dioxide in an air-filled cave, a small amount of mineral -- mostly calcite -- is left behind. Thus, drip by drip, over the past million years or so, Carlsbad Cavern has slowly been decorating itself.
More than 118 known caves are the result of that process. Many formations cling to the ceiling, known as stalactites, while others built up from the bottom, known as stalagmites. Columns formed when the two join in the middle.
A variety of other shapes -- narrow tubes, wall curtains, cave pools, popcorn-like protrusions and occasional pits -- provide the wonder of the caverns.
Each year, about 400,000 or more people visit the caverns, which is roughly the number of summer roosting population of migratory Brazilian free-tailed bats that hang around in their own cave, separate from the public portion.
Just as Jim White discovered, the bat cave is a bit smelly. Despite that, the rangers who host the bat flight at dusk will tell you that the sonar and smelling abilities of each bat take it right to where it perched the day before and right where its young can be found.
The bats at Carlsbad have an 11-inch wingspan, weigh the same as three nickels and use "echolocation" beeps to analyze the echoes that come bouncing back. As many as 300 bats crowd into one square foot, where they hang upside down.
The caverns are spread out enough so human visitors don't feel as crowded. They are open year round except on Christmas.