Mammoth, in Depth

In addition to the cave itself, Mammoth offers 52,830 acres of above-ground activities, including hiking, paddling and fishing. In particular, the north part of the park is crisscrossed by more than 70 miles of backcountry trails, all of them lined with oaks, maples, poplars and other residents of the Eastern deciduous forest. The Green and Nolin rivers also wind through the park for 31 collective miles of waterway.

Paddling the Green in June, my girlfriend, Laura, and I could sometimes spot low-hanging fog at water's edge, a marker of where cool cave water joined warmer surface water. Laura pointed out one such patch early in our trip, and we followed it into the mouth of a small, dead-end cave. Our dog, a liver-spotted Dalmatian named Bella, was on her first canoe trip. She began shivering in terror as we entered the cave, but the little kid in me felt the excitement of discovering a river hide-out. We looked out from the darkness onto the river flowing past, our voices echoing in the dank, chilly air.

Outside again, we paddled past cigar-shaped islands jutting out of the river like battleships. Around us, a handful of people fished from kayaks or drifted aimlessly. I lay back against the canoe's gunwale in a light mist, alternately closing my eyes and gazing at the enormous sycamores arching over the water. It was a lazy, easy, beautiful paddle.

Laura and I were already somewhat familiar with the Green, having pitched our tent in Houchins Ferry Campground on the river's banks. One of three car-accessible campgrounds in the park, Houchins Ferry attracts families wanting to car-camp and fish. When not fishing, their children ran along the grassy riverbank, often playing with Bella, who pranced around them.

But Mammoth's surface activities do not all involve water. Laura, Bella and I also spent a day on the deserted trails looping through the park's northern half, hiking through the shafts of sunlight that penetrated the canopy of maples, oaks and beeches. We saw a grand total of one other person. And even on the ridges, there were hints of the realm below. We paused beside a spring that emerged from the hillside, then trickled over a small, moss-draped waterfall.

Then we looked into the damp pit of a sinkhole, wondering what worlds lay beneath our feet.

Prehistoric tribes first ventured inside the cave about 4,000 years ago, and it is easy to imagine how they might have found the entrance. On a sweltering summer day, the cool underground air pouring out of the "historic entrance" feels like a blast from an enormous air conditioner.

Following the cool draft inside, modern visitors quickly find the ruins of the old saltpeter mines. A bit deeper lie small huts that once belonged to a tuberculosis hospital -- a 19th-century venture that proved better at killing patients than curing them. Another chamber once hosted lantern-light church services.

Along with the sheer size and extent of its chambers, this rich history sets Mammoth apart from other tourist caves. Rather than merely holding forth on geology, guides tell of the African American slaves who served as early tour guides and who rank among the cave's most intrepid explorers. They mention the discovery of ancient mummies, as well as entrepreneurs who searched for new cave entrances by setting off underground charges of dynamite.

For geological reasons, Mammoth has relatively few classic cave formations -- stalactites, stalagmites and the like. But it does have some, and its history and scale easily make up for their scarcity.

Of course, no one tour can include more than a sliver of the world's longest cave. Besides the Wild Cave Tour (which begins miles from the historic entrance), I took the Historic Tour, which covers part of the early tourist route. The trip included mining ruins, a half-acre-size chamber and 440 stairs ascending a 200-foot-tall underground shaft, where water from an outside thunderstorm gave me a quick shower.

Although I sometimes had to crouch on this tour, often I could luxuriate in chambers the size of airplane hangars. Of course, some people won't consider a cave chamber, no matter how spacious, as grounds for luxuriating. I can only say that these people have never been on the Wild Cave Tour. Think of an enormous performing arts center -- grand halls, beautiful auditoriums and some good artwork on the walls. Now imagine exploring it via the air conditioning ducts. This should give you an idea of what Mammoth's Wild Cave Tour is all about.