Civilization has come a long way since some prehistoric ancestors sheltered in caves, but these chilly, damp holes in the earth continue to fascinate.

Mammoth Cave, in southwestern Kentucky, was one of America’s first international tourist attractions, opening to the public in 1816. Niagara Falls was the only attraction to outrank it.

Kentucky has more than 3,000 known caves and about seven show caves. Most caves are under private property and thus have private ownership. In fact, Mammoth Cave, the longest at more than 400 mapped miles, is only partly under national park land. The rest belongs to landowners above ground.

In three days visiting southwestern Kentucky, we visited three caves and had distinctively different experiences because of cave composition and crowd size. Small crowds are better for both listening and asking questions.

Our first experience was Hidden River Cave, in the 2,200-population Horse Cave. It is owned by the city and operated by the nonprofit American Cave Conservation Association. It starts with a 173-step descent down a stone stairway into damp, earthy-smelling cave air. In a well-lit hike through spacious passages, visitors find themselves 150 feet under city streets, where the temperature is in the 50s year-round.

At the cave opening, the tour guide paused to talk about history. American Indians used the river cave for its clean water and other resources. In the late 1800s, a private European owner began selling freshwater from the river. Then, in 1916, the stone steps were built, the first electric lighting was installed and it opened to the public.

After showing off rusty remnants of the early electricity-generating equipment, the guide got sadly serious about pollution that shut down the cave in the 1940s. Lacking a sewage processing system, local land, sewers and industry dumped into the lowest point, the river. It wasn’t until the 1990s, with pollutants removed from the cave and a regional sewer facility in place that tourists could return.

The makeup of this river-cave is such that it lacks stalactites, stalagmites and other structural formations. Instead, visitors see domes — vast open rooms — up to 2 acres large and 80 feet high, as well as cave-dwelling crickets and blind crawfish on the tour.

At the entrance a 280-foot long, 75-foot high zipline and 75-foot rappel line into the sinkhole offer beginner-level adrenaline rushes. Those seeking more adventure should sign up for three- and five-hour wild cave tours that go over the river and through narrow crawl spaces into some of the 10 miles of mapped passages.

Diamond Caverns in Park City — population 550 — is halfway between Louisville and Nashville. The privately operated cave system offers a one-hour, half-mile guided tour of a frequently wide natural but occasionally narrow tunnel full of American history and travertine (“traveling rock”) limestone formations such as stalactites and stalagmites. We went with a group of six. It was a treat to have almost exclusive attention from the guide for questions and information.

Our tour started through a gated man-made entrance just off the gift shop. The cave has 350 steps, though no more than 50 at one time.

The original cave was discovered in July 1859. By August, enterprising landowners were charging tourists to take lantern tours of the same cave. Lantern tours, as our guide demonstrated, weren’t nearly bright enough to fully appreciate fantasmic rippled surfaces that appear designed by architect Antoni Gaudi or author Dr. Seuss. While some rock formations resemble dripping candle wax, other times calcite crystal layers play light like diamonds (hence the cave name).

The tour group first encountered 13-foot haystack formation. After that, the hits kept coming — cave bacon, popcorn, coral, honeycomb. Graffiti scratched into the soft stone has been dated and verified as evidence of both Confederate and Union soldiers during the Civil War.

After 30 minutes, the tour reverses. Even though we covering the same ground, everything looked new.

Mammoth Cave, in the heart of a 53,000-acre national park, was the most famous of our three underground adventures. At the time of writing, it had 405 miles of mapped passages, but that could change any day as it’s continually under exploration.

Every year a half-million people buy tickets to at least one of the park’s 14 cave walks. Among them are Wild Cave and Accessible Cave tours, which take limited groups. Some tours are offered multiple times each day, with up to 40 tours per day during peak season.

It was first opened to the public in 1816, 100 years before Hidden River.

During this tour, guides used lard-oil lanterns to cast light and shadows through the passages. Details were not nearly as visible as today with electric lighting.

We started the Domes and Dripstones tour at the “New Entrance,” created by a private owner in 1926. With our group of 115 was 7-year-old Kriztofer Thompsett, my cousin’s grandson, who lives an hour north in Elizabethtown. While I couldn’t hear the guide at the front of the group, I enjoyed Kriz’s childlike wonder at every dark passageway and haphazard rock pile.

“That’s a whole lotta nature,” Kriz pronounced as he hopped down 280 steps in the vertical cave where we began.

While adults were ducking and gut-sucking between tight cave walls, Kriz merely wiped a few water drips from his straight red hair and clambered downward to Grand Central Station, a large chamber at the bottom. The guide waited for our melting pot of humanity to settle onto wooden benches roughly 240 feet below the surface. There she explained cave formation and told us that “breakdowns” or falling rocks had never hit tourists.

We walked through dry passages of rock, observing piles of breakdown and dark passages on both sides. Above us, the ceiling resembled the unpainted plaster surface of an abandoned home. Kriz was full of “I wonder” statements, including “I wonder what would happen if there were no lights. I wonder what would happen if rocks fell.” That last didn’t help with my claustrophobia.

After an hour, we came to our first formation, the most dramatic known in Mammoth Cave, the Frozen Niagara. It looks like a frozen waterfall, but it’s solid rock formed by water that came in slowly over thousands of years and dripped over a ledge to make the shape. There were optional 49 steps down and up to wonder at the 75 foot structure. That was followed by stalactites, stalagmites and columns behind railings to prevent curious fingers. All too abruptly, we hit the revolving door to the bus stop where we met our ride back to the Visitors Center.

While we spent 90 minutes underground (and another 30 ferrying between the Visitor Center), Kriz’s grandparents were taking an accessible tour. They descended 267 feet, almost 27 stories underground via a seven-person elevator and covered a half mile with Grandpa pushing Grandma in a wheelchair (she had a broken foot). The accessible cave, which just reopened in October, has level passageways that are easy traveling for wheelchairs and scooters. The two-hour trek is void of claustrophobia-inspiring tight spots and offers both water and restrooms.

Whatever the tour, I recommend sticking close to the guide for information or at least taking a child for interesting narrative.

GETTING THERE

Getting to the cave-rich area of southwestern Kentucky takes eight to 10 hours from Northeast Ohio by freeway. Getting from cave to cave can be an exciting experience by narrow, hilly, twisty back roads with no shoulders. Cave visitors should be prepared with comfortable walking shoes that can handle slippery surfaces, as well as sweaters or jackets if they find 50-degree temperatures uncomfortable. Most tours are one to two hours, include stairs and lack restrooms. Some require squeezing through spaces only one foot wide, and most require ducking by folks more than 5 feet tall. Those uncomfortable with these restrictions should consider the accessible tour.

Cave tours should be reserved in advance. Camping is popular in the area. With advance planning, cabins can be reserved. A few motels are available at freeway exits.

Diamond Caverns: diamondcaverns.com, 1900 Mammoth Cave Parkway, Park City, Kentucky, 270-749-2233

Hidden River Cave: hiddenrivercave.com, 119 E. Main St., Horse Cave, Kentucky, 270-786-1466

Mammoth Cave: www.nps.gov/maca/index.htm, 1 Mammoth Cave Parkway, Mammoth Cave, Kentucky, 270-758-2180