Fresh air, exercise and an art bridge

The other night, I did something new and possibly stupid: I rode my bike on an unlit trail through rural Iowa. It was dark, except for the dim beam from the cheap flashlight I jury-rigged to my handlebars and the occasional flickering light of passing bikes. It was quiet, except for the periodic rustling, croaks and calls of who-knows-what. It was spooky.

So after riding a few miles, I was pleased to see a burst of white and blue light off in the distance. The Bridge!

And as I pedaled slowly across that 1/2-mile long, 13-story-high bridge -- its span dotted with white lights and its square-shaped arches lined in blue light -- I realized this was the coolest experience of my 20 years riding Iowa's beloved recreational trails.

This revelation, no doubt shared by others, also helps explain the enormous popularity of the High Trestle Trail, a 25-mile paved trail near Des Moines whose final and most impressive stretch, including the bridge, opened in spring 2011. It has lured thousands of visitors and kick-started businesses catering to out-of-towners on bike, foot, Rollerblades and horseback.

Before our night ride in May, my husband and I had enjoyed biking various segments of the trail by day. Converted from a former railroad bed, the trail runs between Ankeny, a Des Moines suburb, and four small towns to the north and west, Sheldahl, Slater, Madrid and Woodward, about 237 miles south of the Twin Cities. The trail's first 23 miles opened in fall 2008.

Largely flat with easy pedaling (although crosswinds can make it feel more like resistance training), the trail includes long stretches through classic Iowa countryside, with sights both bucolic and prosaic: a farmhouse on a gravel road, fields sprouting green shoots of corn, enormous John Deere combines, a cow standing in muddy water.

We like picnicking in the sleepy little park in Sheldahl (pop. about 317), with its fold-up bandstand, and visiting the Town & Country Market inside an ivy-covered brick building in Slater's two-block business district.

During our day rides, we have always been bowled over by "the Bridge." Billed as one of the world's largest trail bridges, it offers spectacular 5-mile views of the Des Moines River winding through a wide grassy valley with tree-lined sandy bluffs.

We love the reconstructed bridge's sculptural flourishes, which pay homage to the area's coal mining past.

Flanking the entrances are 42-foot limestone towers veined with black bands, representing seams of coal. Laid out at rotating angles are 41 square-shaped arches that form an open-air tunnel, representing the cribbing that supports a coal mine shaft. (At night, a section of the arches is lit in blue, intensifying the fun-house effect.)

The bridge's overlooks have informational panels highlighting the area's cultural and natural history. So does an adjacent lookout on what little is left of an earlier bridge the railroad built in 1912, high atop steel posts and crossbeams, aka trestles (hence the trail's name). The current bridge is a do-over of a 1973 railroad bridge built atop 130-foot concrete piers.

This time, though, beginning our ride at 5 p.m. on a Saturday -- so we'd be at the bridge by about 9 p.m. -- added much more drama. It wasn't just the adventure of getting to the bridge as night fell. The pink, blue and yellow sunset literally cast the landscape in a different light.

We also timed our 24-mile roundtrip ride between Woodward and Slater so we could linger at two trail-side bars, the Nite Hawk, which opened in March in Slater (try the homemade potato chips), and the year-old Flat Tire Lounge in Madrid.

At both, spandex-clad cyclists crowded around outdoor tables, reminding me of the proudly sweaty riders during RAGBRAI, the "[Des Moines] Register's Annual Great Bike Ride Across Iowa." Minnesotans made up 5.5 percent of 2011's 10,000 riders, the third largest state group, and the High Trestle Trail was a popular side trip. The route for this year's 40th RAGBRAI in July didn't go as close.

Because no roads lead to the bridge and because it's in the middle of nowhere -- midway along the trail's western-most 5.6-mile stretch between Madrid and Woodward -- the journey to get there feels like you're on a pilgrimage to a hidden shrine, especially in the still of night as you encounter other cyclists and walkers heading the same way.

Most people had lights (often stronger than mine) but a few didn't, making them hard to spot until they were unnervingly near. But somehow we all ended up on the bridge, with a full moon above us and the vast shadowy valley below, part of the awestruck crowd.