BIG BELT MOUNTAINS -- Tucked high on the southern wall of Trout Creek Canyon, the Hanging Valley offers sweeping views of the cliffs northeast of York -- towering chunks of limestone formed 250 million years ago and later thrust upward in the massive cataclysms that formed the Rocky Mountains.

The Hanging Valley National Recreation Trail is a moderately strenuous path that takes hikers and mountain bikers up over a ridge and down into a narrow, high-walled canyon.

After scrambling beneath an uncommon limestone arch, folks find the trail's end at the lip of a dry waterfall, easily 500 feet above the trees of Trout Creek Canyon. A heavy fence at the edge gives some assurances to those wary of heights -- and the views are superb.

I've done the hike twice now, each time taking little more than six hours from start to finish. Guidebooks and signs say the out-and-back route is 12 miles, and after some hemming and hawing, I think they're right.

I like the way this trail is laid out -- with a long, steady climb to the top of the ridge at the beginning, which gets the only real work out of the way right off the bat. A few open spots along the top of the ridge offer wide-ranging views of the Big Belts, Elkhorns and the Continental Divide.

Then the trail drops down into Hanging Valley via a set of switchbacks, followed by an easy downgrade. The final leg is a visual treat, with the cliffs growing taller and the canyon narrowing until the walls are almost arm's-length apart. The path is loose and graveled in the bottleneck just before the end, so some hikers may want to consider using poles.

Older or unsteady users might need a hand getting down the final steps to the overlook and back out again, but the sight is truly worth seeing. A few lookouts at the north end of the little valley are real cracks in the wall, and offer a slightly more harrowing perspective.

The hike out is easier, with a quick swing up through the switchbacks and then a long, winding downgrade back to the trailhead.

Weather can change quickly in canyon country, so come prepared with rain gear. There's no water at all on the trail, so bring plenty. My first trip through was later in the season, and I ran into some bugs in the valley. This trip, taken a few weekends ago with friends, was bug-free. We found some snow in the narrowest part of the canyon, but it was easily passable.

The Hanging Valley, Trout Creek Canyon and some of the surrounding landscape are part of what's known as the Montana Overthrust Belt, according to Beth Ihle, a geologist for the Helena National Forest.

Sedimentary rocks buckled upward (think of an upside-down U) under tremendous forces as the North American and Pacific crust plates collided some 70 million years ago.

The massive shifts caused cracks and weak spots in the rock, which have eroded through the millennia, creating the startling views visible today.

"And so these massive limestone rocks ... in some places, they are sitting upright and in other places, they're standing on end," Ihle said. Other rocks were tilted or folded under the pressure. "For geologists, we would say this area has been massively deformed.

"In Hanging Valley, you have two primary overthrust faults that have buckled the limestone layers on top of each other, kind of like dominos. It was a zone of fracture and cataclysmic activity.

"What a cool spot," she added.

The rock arch differs from similar formations in the Southwest, Ihle said, because it consists of limestone rather than sandstone.

"To have an arch form in limestone, considering how many internal fractures those things have, it's pretty amazing," Ihle said. "You don't see a lot of arches in limestone."

Getting there

Take York Road to York. Stay on the road, which eventually turns to gravel. It dead-ends at the Vigilante Campground and the Trout Creek Canyon trailhead. Park here and walk to the southeast side of the campground to locate the Hanging Valley trailhead. The trail is Forest Service 247.

National Trail Day

American Hiking Society and outdoor enthusiasts across the country will celebrate the 17th annual National Trails Day this Saturday.

The event marks a long-standing celebration of America's trail system and the countless supporters and volunteers who help maintain it, such as those working with the Prickly Pear Land Trust and the Bob Marshall Wilderness Foundation.

More than 1,500 events will take place around the country including trail maintenance, hiking, paddling, biking, horseback riding, bird-watching, running and trail celebrations.

In the coming week, these events are planned in the Helena area:

On June 13, the Dirt Divas will host their day-long mountain bike clinic and ride in Helena. For more information call 442-4644.

Also on June 13, the Helena Bicycle Club will host its Double Divide Ride, following some great routes across the Continental Divide. Call 439-8379 for more information.

On June 26, during the Mount Helena Music Festival, the annual Trail Fest kicks off. Call 443-5188 for more information.