Continued: Ultrafit: Conquering the 'Marsh Mountain'

We're in a field near Shakopee, a mile east of the Minnesota River on the prairie at Louisville Swamp. The park, a 2,600-acre unit of the Minnesota Valley National Wildlife Refuge, sprawls north through tall grass and oak trees, a dirt trail dipping downhill to a flood plain and the preserve's namesake mile-long swamp.

The big rock on the prairie -- a glacial erratic, almost 15 feet high and more than 100 feet around -- is an anomaly on the pan-flat land. But then so are Getzke and his crew, a group of buff-armed climbers practicing a mountain sport at the edge of a swamp.

"Watch me!" Getzke shouts, signaling a spotter to step close. He's 8 feet off the ground, climbing unroped and about to fall. His feet play on an edge, stepping, feeling steep stone for purchase. Dust spits off into a sunbeam when his shoe slips.

"You've got it, man!" shouts Connor O'Brien, a climber watching from below.

It's a Tuesday evening in mid-May, and Getzke, a 54-year-old inventory manager from Bloomington, has invited a half-dozen friends to climb at Louisville. The evening's discipline of choice, a climbing style called bouldering, leaves ropes and carabiners out of the equation, employing instead foam crash pads placed below routes to soften impact in a fall.

Like most of the climbers present, O'Brien, 24, from St. Louis Park, has visited the state's popular climbing venues but only recently heard of Louisville. "You hike around the corner and, boom!, there it is," he said of the boulder, which sits startlingly alone on the prairie.

Geologic exception

On the trail map for Louisville Swamp, the Big Rock is marked simply with the name "Glacial Boulder," and there is no mention of the erratic (a term used for non-native pieces of stone) on the Web page for the park. But in addition to being the closest real rock for climbers in the Twin Cities, the big hunk of stone is a geologic rarity.

According to Peter Hudleston, a geology professor at the University of Minnesota, the Big Rock probably traveled 100 miles or more during the last Ice Age to reach its current resting spot. The chunk was picked up and carried by glacial ice and left stranded with other sediment when the ice sheet melted. "Smaller particles were washed away by glacial River Warren, which drained Lake Agassiz [in what is now Manitoba, Canada] 10,000 years ago," he said.

Hudleston, who specializes in structural geology and tectonics, said there are few local glacial erratics as prominent as Big Rock. "I've not seen anything else this large in the area," he said.

As a longtime Twin Cities climber, Getzke first heard about the Big Rock in 1998 when he read an article in Vertical Jones, a now-defunct local climbing magazine. "I saw the story and drove out to Shakopee the next day," said Getzke, who was known to climb on area bridge abutments before discovering Louisville.

He now heads to Big Rock several times a month, skiing in to climb in the winter and slapping bugs at the edge of the swamp in the warm months. Chalk marks on the rock have signaled the presence of other climbers, though Getzke said he rarely encounters people on the prairie. "It's been my own private climbing area," he said.

Climb time

During the evening session last month, Getzke led the hike in, tromping west from a gravel road and through the woods. I stuck with Michael Shomsky, 48, of Minneapolis, who wore a backpack, his climbing shoes clipped on the outside with a carabiner. "This path ahead was flooded last week," he said, pointing to an old track dipping near a pond.

We walked for 10 minutes, climbed a small hill and stopped where the track, called Middle Road, intersects the park's main loop, the Mazomani Trail. The Big Rock, a gray and black bulk, larger than a city bus and approximately the same shape, sat out in the open past some trees.

"Wow," said John Peacock, a first-timer to the park. "It's huge!"

In two minutes Shomsky and Getzke were on the wall, reaching for cracks and knobs, traversing the west face, then pulling over the top to complete a climb just higher than a basketball hoop.

O'Brien and Peacock moved in to put hands on the smooth face, looking up to decipher a difficult climb. "This is just a classic move off the gaston," Shomsky said, referring to a small sideways handhold at the base of the boulder.

The sport of bouldering, which has a small following in Minnesota, concentrates on steep or overhanging routes often less than 10 feet tall. The climbs -- called boulder "problems" -- skew toward the expert end of the scale, with long reaches, minuscule holds and tough sequences requiring strength, balance, flexibility and concentration. "Bouldering is the poetry of mountaineering," Getzke explained. "Short and difficult."

At Louisville, where an orange sun sank into the trees, the climbers danced and swung on the rock. Getzke tiptoed up a corner; Shomsky lunged for the top, a sloping nose with texture and grip.

Peacock pulled off the ground, then fought gravity on a route above his ability. "Where should I put my foot?" he shouted, eyes racing, his shoes slipping on the stone before -- hhuumpff! -- a crash on the pad below.

From the trail, the Big Rock framed a view to the east, the sunset shining over blue sky turning dark. Getzke stood on top, looking over the edge, shouting encouragement to the smaller-appearing climbers below.

Bugs buzzed in the bushes. Shapes climbed beyond in orange light. Movement and poetry at the edge of a swamp.

Stephen Regenold is a Twin Cities writer and author of the syndicated column www.thegearjunkie.com.