Spend enough time in this neck of the woods and you're bound to find out what makes Kentucky tick - limestone and history. Practically everything associated with this semi-Southern state - bluegrass, thoroughbred horses, and caves - is built literally on a bedrock of limestone.
And that is history. A lot of the rock is 300 million years old - perfect timing when it comes to carving caves (some of the world's largest) underneath the green fringe of the Appalachians, but a tad too early to catch the really interesting stuff like Jenny Lind singing ''The Last Rose of Summer'' 500 feet underground, the Emperor of Brazil and the Grand Duke of Russia eating supper in the subterranean dining room, or Jesse and Frank James holding up stagecoaches outside Cave City.
Even in the 20th century there have been some wild times here. When Floyd (The Lad) Collins got stuck in Crystal Cave for 18 days, it created the biggest rumpus in these parts that anyone remembers. The National Guard was called in to keep the spectators and press at bay with pointed bayonets. Even so, ''Skeets'' Miller, a Louisville Courier-Journal reporter, won a Pulitzer Prize for his coverage of the spelunking catastrophe and, presumably, his gallant, but ultimately fruitless, attempts to free Floyd with a car jack.
Since then, happenings in cave country have been a bit more tame. Local railroad lines rusted into disuse, as did the steamboats that paddled up and down the Green River ferrying the curious from Bowling Green and Evansville, Ind. Students from Ohio State University wrote O-S-U on the limestone cave walls , not with spray paint, but with historically accurate cane torches. Much later, less indigenous Alpine Slides and Jellystone Campgrounds and souvenir ''Rocks for Less'' shops would spring up. But by the time Franklin D. Roosevelt had hit his third term as President, this purported Seventh Wonder of the World was officially legit - Mammoth Cave National Park. And perhaps that was the best news of all.
Probably more kids than anyone cares to number have been dragged through these giant underground caverns, now protected by the Interior Department and UNESCO. (Mammoth Cave is a World Heritage Site.) Most people you talk to - especially if they grew up in Michigan or thereabouts - will tell you they paraded through Mammoth Cave years ago on any number of family car trips to Florida. Moms and dads were presumably more interested in the geological aspects and thought it would make the perfect spot to stretch the legs.
They weren't too far wrong. There are nearly 300 miles of caves already mapped and explored, and experts expect to chart another 200 miles or so. Of course not all that acreage is open to public, but even the chance to walk for four miles underground has a particular appeal.
And not just for tourists. A recent Courier-Journal headline trumpeted the fate of some locals who went out for a midnight cave jaunt: ''Hoosier brothers find life's the pits at bottom of 40-foot hole in cave.''
The saying around here is that ''caving gets in your blood.'' Many of the smaller caves have been privately owned for generations and are coveted sources of family income. Even if a local resident is just a cave guide, there's more than an even chance that somebody else in the family was a guide, too. Caves are big business here. They are also an indelible part of the state's heritage. Strolling through any part of Mammoth Cave is like hyperbole come to life: walking through history.
But first a word for geology. Actually you need to know only three things to have a good working knowledge. As Don Lindsay, a park interpreter, explained, ''limestone, river, and tilt - that's what's caused the caves.'' It's a rare combination. Borneo and France are thought to be the only other sites to have rustled up the geological ingredients to such a degree.
While rockhounds may enjoy learning the specifics of St. Genevieve Limestone, Girkin Formations, and geology's Tertiary Period, most lay folks will be happy to know that sometime during the Ice Age slightly acidic underground water, rushing toward the Green River across beds of limestone buried beneath an insoluble sandstone cap, created the longest dry caves in the world.
While most people think of caves as tight, body-squeezing passageways dripping with water and populated by bats and opalescent stalactites, not so Mammoth Cave. Thanks to that sandstone cap, surface water is kept at bay and the underground tunnels sit high and dry. Frozen Niagara is the only park cave dripping with stalactites. (Nonetheless, underground water continues to drain through the deepest part of the cave, and park officials are increasingly concerned about water pollution.)
If you think this sounds dull - like sightseeing in a parking garage - well, you haven't had your cave ''interpreted'' correctly. A rich, mellifluous Kentucky drawl rumbling on about Mr. Houchins chasing a bear into the cave mouth back in the late 1700s can make all the difference. At least it did for me.
Dressed in regimental ranger khaki and brushed felt hat, park intrepreter Lindsay led me, in deck shoes and blue blazer (I'd advise against the blazer and in favor of deck shoes) on my first-ever visit to a cave. We took the Historic Tour. It's one of several available here, and it is true to its name. It's a two-mile, two-hour jaunt over modest hypogeal hill and dale. And a veritable walk through the centuries. First off I learned the mystical origins of the cave's discovery - Mr. Houchins's fateful bear chase - that revealed the only natural entrance to Mammoth Cave. (The others have all been the result of dynamite.) Of course, Pre-Columbian woodland Indians had known about and used the caves for previous decades untold - there is rock-hard anthropological evidence for this - but Houchins was the first white man inside. Or so goes the story, and there are a lot of stories to be told.
Like the one about the cave-mining operation that supplied 60 percent of the all the American gunpowder used in the War of 1812. You can touch the cool rocks worn smooth by the tethered oxen that waited patiently to haul out the cartloads of soil rich in nitrates from bat guano.
Next I learned from Ranger Lindsay that ''the lights do go out, so we always bring a flashlight.'' We are walking through Rotunda - 140 feet underground and one of the largest rooms of the cave - 50 feet high and 60 feet wide and lit, as it happens, by fluorescent fixtures. As if to prove his point, he flips a nearby switch and we are plunged into impenetrable darkness. ''Yikes'' is the word that springs immediately to mind, followed in a moment by the question, ''Who in their right mind would come in here without benefit of General Electric?'' ''Someone who was brave or didn't know very much,'' says my guide in response to this apparently common query.
He lights a cane torch - cotton rags wound around a hickory stick - and flings this native luminary up into a high crevasse. ''That's pulpit rock,'' he says, pointing to the exceptionally craggy stones and flickering shadows. ''In 1835 they held church services in here. Nowadays, somebody on a tour will sing. Sounds good in here.''
''Over there,'' he says, pointing in the direction of what looks like a side street, ''is Devil's Arm Chair.'' It's the site of Jenny Lind's performance. Did she sit in the chair during the performance? ''No, ma'am, I believe she stood,'' Lindsay politely answers. In 1876, Edwin Booth, the actor and brother to John Wilkes Booth, also gave a performance here - Hamlet's ''To be or not to be'' soliloquy. Was Booth here for a centennial celebration? ''No, I believe he had just come to visit the cave. After the assassination he was sort of out of circulation.''
We stroll on down Broadway Avenue, the largest passageway in the cave. It becomes Gothic Avenue, where, I am told, weddings were held during the peak of cave popularity, right after the Civil War. As time went on, other caves opened up, which is more than can be said for our next encounter - Fat Man's Misery - a belly-scraping passageway in the cave which children apparently love but adults apparently do not. ''Sometimes people do get stuck in here,'' Lindsay says, pushing on through the curving limestone.
''Fat Man's Misery'' is followed by, what else, ''Tall Man's Misery'' - a footpath roofed by a particularly low-slung ceiling. This mercifully opens into the soaring, dome-shaped Great Relief Hall. It's apparently named for its welcome height, but today it includes restrooms and a drinking fountain.
We are working our way gradually downward and also back toward the mouth of the cave. ''There are 294 miles of connected cave, but no one as far as I know has ever walked the whole way,'' says Ranger Lindsay, striding on past something called ''Bottomless Pit.'' It is possible to walk a good four miles on the strenuous ''Half Day Tour.'' This jaunt takes the intrepid by such enticingly named cave formations as the Frozen Niagara, Grand Central Station, Grand Canyon , Rock of Gibraltar. ''Things were labeled with names people might be familiar with,'' Lindsay explains.
There is also a stop for lunch at the underground cafeteria - the Snowball Dining Room, named for the white, gypsum-encrusted ceiling - before continuing on past the Black Hole of Calcutta, Ole Bull's Concert Hall, Shakespeare's Galleries, Sahara Desert, and eventually emerging, like some marathon mole, at the Historic Entrance.
I am almost tempted. I'd like to catch a peak at the eyeless fish, first discovered in 1842 in the underground Echo River, and any of the 300 other species of cave flora and fauna discovered here. But the faint stirrings of a cool breeze signaled our approach to the entrance.
Blinking in the pale afternoon light, we emerged in what seemed a leafy paradise after the dim, rocky recesses of the cave. It was a feeling like no other I had ever encountered. I felt as if I'd crawled inside my planet - and not simply walked on its back. That I had marched down to the earth's limestone innards and found them rich with their own history as well as the paths of men. Even the hickory trees, wagging in the breeze, looked better for this journey.
I wondered if Jenny Lind and Edwin Booth or even the Hoosier brothers had felt the same way. Ranger Lindsay seemed to read my thoughts.
''I'd rather be working in the cave than outside,'' he said, squinting into the Kentucky sun. '' 'Cause when you're home you can have all the outside you want. But you can never get all the cave you want.''
Mammoth National Cave Park is about 80 miles south of Louisville on I-65, near Cave City. With more than 400,000 visitors a year - 60 percent arrive in June, July, and August - reservations are recommended and are available through Ticketron. A visitor center is open daily 7:30 a.m. to 7 p.m. in summer and 8 a.m. to 5 p.m. in winter. Tours, leaving the center every 15 or 20 minutes, vary in length and price and demand good walking shoes and a willingness to occasionally scramble. One tour has been designed for those in wheelchairs.
For the nature buff and serious hiker, the 52,000 surface acres provide an alternative to spelunking. They deserve exploring. There are numerous campgrounds and hotels in and near the park.
For reservations and information write Superintendent, Mammoth Cave National Park, Mammoth Cave, Ky. 42259, or phone (502) 758-2328.