For his love of caves, John Ackerman has fallen into deep pits, nearly drowned in an underground stream and barely escaped being crushed by tons of rock.
It's no wonder that his wife insists on a $2-million life insurance policy.
Over the last 16 years, Ackerman has spent more than $1 million buying and digging up southern Minnesota farmland in search of caves unseen by human eyes. With his trusty modified track hoe, "Cave Finder," he's discovered or expanded 19 caves on his 325-acre plot in Fillmore County.
His Cave Farm is considered one of the largest privately owned cave complexes in the United States. Yet it's virtually unknown to the public because he's made no effort to commercialize it and doesn't intend to.
Nonetheless, his aggressive tactics -- constantly unearthing farmland and using explosives -- draws the ire of some. To others, he is a conservationist who generously opens his caves to explorers. Friends describe him as a hard-charger.
"You don't feel neutral about John Ackerman," said friend E. Calvin Alexander Jr., a University of Minnesota hydrogeology professor. "You either think he's an amazing individual or you think he's the worst thing that's happened to caving since I don't know."
An avid cave explorer since he was a boy, Ackerman, 49, says he grew frustrated in the mid-1980s when many of Minnesota's best-known caves began limiting access or refusing entry. Many caves closed because owners feared litigation if someone got hurt. Others were turned over to state or federal authorities, who limited access.
That's why Ackerman says he went to great expense and battled neighbors and other explorers to find his own caves.
"You're walking through a slice of time," he said as he surveyed an excavated sinkhole that recently became his 19th cave. "To be the first human being to explore them is pretty much why we do it. And once we have discovered them, they're going to be here forever. They're going to be known, studied, photographed."
When he's not running his furniture-restoration business in Burnsville, Ackerman and "Cave Finder" can be found scooping out sinkholes in search of darkened dirt or white-spotted stones -- telltale signs of moisture that can lead to cave entrances. Once a cave is found, he sinks a shaft to serve as a safe entrance.
Warren Netherton, a cave specialist with the Minnesota Department of Natural Resources, says he's disheartened by the lengths to which Ackerman has gone to become the most famous caver in the Upper Midwest.
Ackerman, he says, is infamous for "scooping booty" -- running down passages so he can be the first to lay eyes upon a cave. That breaks an unwritten rule among cavers that new passages be surveyed along the way rather than rushing through.
Ackerman offers no apologies. "When my dad died, I got nothing and a wrench, so anything that I've done, I've worked extremely hard for," he said.
He disputes the idea that he should wait until nature reveals caves, a notion he contends is not likely to happen in his lifetime. "We're going to dig out all the soil and find the cave, and then we're going to protect it."
The Cave Farm originated with a single half-mile cave discovered in 1966 by a farmer who was searching for a lost calf. The farmer decided to commercialize the cave, dubbing it Spring Valley Caverns, and adding electricity and stairways.
But the venture failed, forcing the farmer into bankruptcy. Another farmer took over, closing the cave and all exploration activities until 1983, when a new owner allowed access to some members of the Minnesota Speleological Survey.
About the same time, Ackerman was trying to find new passages in nearby Mystery Cave, the state's largest cave at 13 miles long. Through a friend, he heard about the dormant Spring Valley Caverns and the numerous sinkholes that laced the property.
On his first visit, with the owner's permission, he found two caves. A few years later, he bought the farm and used explosives to break through and discover miles of passages within Spring Valley Caverns, which now stretch nearly six miles.
Since then, Ackerman has studied excavation and engineering so he could unearth 18 more caves and build entrances.
Streams, waterfalls, stalagmites, stalactites, soda straws, "dripping" stone and a petrified bat are some of the treasures that he's discovered in the nine miles of caves under his property, which is within the karst region of southeastern Minnesota. Experts say the Cave Farm was probably created over millions of years as water sifted through the soil, dissolving the 450-million-year-old limestone.
For Ackerman and his friends, half the fun is mapping the caves once they're found. They've nicknamed each passage in Spring Valley Caverns -- there's Jimmy Carter Junction (a peanut-shaped hall) and the Upchuck Room (where lost raccoons had been ill).
For cave connoisseurs, Ackerman is a blessing.
Allen Lewerer, president of the Minnesota Speleological Survey, says that although some may question Ackerman's approach, none can dismiss that he has opened a new vein of caves and keeps them in pristine condition. The University of Minnesota tapped his caves for a water-flow experiment this fall. Researchers want to know if water from one river goes to another through underground streams.
"He's really fortunate that he has the financial backing that he can do this. More power to him," Lewerer said. "But he is also very cave-conscious. It's kind of one of those things -- break bones, not formations."