Take the Louisiana Superdome and bury it deep in the heart of a mountain. Send an underground river raging past the home team's bench, carving away that side of the field until a deep canyon yawns where once the New Orleans Saints watched their postseason dreams slip away. Leave a rocky overlook on the visitors' sideline. From the rafters two hundred feet above this spot, hang a nylon climber's line about the diameter of your middle finger. Let it dangle and sway. Now imagine a narrow ledge from which you can grab the top of this rope, and you'll have a, pretty good picture of where I am. Or soon will be.
I'm lying on my side, inching through a narrow gap between walls of solid limestone. Over the past hour I've rappelled down a 68-foot pit, climbed two waterfalls, crawled several hundred feet along a subterranean streambed lined with shin-bruising cobbles, shinnied up and down and across stone fissures and squeezed through a hole the size of an office waste-basket to reach the rope beyond the gap.
The other end of the rope rests on the floor of one of the largest underground chambers in America. Beyond it, a river of pure spring water, brimming with exotic life, flows through mile upon mile of enormous cave passages. All of this was discovered within the past five years. And all of it was kept secret by the small team of explorers who had found it—until the entire cave was threatened by the construction of a $6.5 million sewage plant just upstream, and the secret was revealed in an effort to head off an environmental catastrophe.
Fatigued after only an hour underground, I might turn tail and clamber toward the sunny Tennessee day taking place overhead—if not for the voice coming from a wide spot in the passage between me and the big drop. The sound is a melodious mixture of backwoods inflections spoken deliberately, in the manner of a Confederate field commander from central casting. To U.S. cavers—especially those familiar with the cave-rich region called TAG, an acronym for the intersection of Tennessee, Alabama and Georgia—it's the voice of a legend. "Get a move on, fatso," says the voice. "Don't just lie there a-lollygagging."
I look up at the gaunt, angular frame of Marion O. Smith, one of the discoverers of the Rumble Room—the Superdome-sized chamber just ahead—and the principal explorer of Rumbling Falls, the sprawling 15.7-mile cave system connected to it. Smith reclines against a boulder. His scraggly off-white beard remains mud-free, as do the wisps of reddish-white hair curling from beneath his battered helmet. Most of the eight other cavers on this trip wear brightly colored, pricey nylon coveralls, but Smith is dressed in brown thrift-shop trousers and a mud-colored long-sleeved shirt.
If caving were a professional sport, Smith would possess the lifetime stats of a Wilt Chamberlain or Ted Williams. As of Sept. 24, his 60th birthday, he had explored 5,182 wild caves and rappelled into 2,762 pits more than 30 feet deep. Unlike a pro athlete, though, Smith has achieved some of his greatest feats in middle age. He wears out twentysomething super-cavers as he penetrates virgin passages in the hills and hollows of TAG and as far away as central Mexico.
A native of Fairburn, Ga., Smith first ventured beneath TAG in 1965. A student of the antebellum South, he also developed a passion for caves that were decidedly un-virgin. The soil of Southern caves was mined for saltpeter, a key ingredient of gunpowder, from the American Revolution through the Civil War. Because saltpeter caves tend to be dry, the wooden vats and tools left behind by early miners were often remarkably well preserved. Smith's expertise in the history of this era helped secure him a job at the University of Tennessee as assistant editor of 16 volumes of the papers of Andrew Johnson—a job from which he retired in July 2000.
Smith has won the Lew Bicking Award, the highest honor for cave exploration, bestowed by the 12,000-member National Speleological Society (NSS). But he has the kind of personality that also prompted one TAG caving group to bestow on him—twice—an entirely different honor: the Horse's Ass Award, a cookie shaped like a hand with an upraised middle finger. " Marion can be difficult to be around for extended periods," one friend confides. "He has no tolerance for fools."
The Cumberland Plateau resembles a vast layer cake set down in middle Tennessee. Thick cave-rich beds of limestone are stacked atop one another and capped by a thin icing of sandstone. Along the edges of the plateau, great wedges have been carved out by water, creating steep-walled valleys called gulfs, each named after the creek that drains it. Fall Creek Falls, the highest aboveground waterfall east of the Mississippi and the central attraction of its eponymous state park, flows into such a gulf.
In times of heavy rain the creeks become dangerous Whitewater torrents, but most of the year they are bone dry. The water vanishes underground, through gravel beds or, occasionally, large swallets that pull streams in like bathwater down a drain. Cavers have long known that underground river systems must carry this water to the distant springs where it resurfaces, but most of these rivers have eluded human exploration. It's relatively easy to find virgin caves along the edges of the plateau, but they are usually small and unremarkable.