Sledding at Great Sand Dunes National Park

The sun is glinting brightly off the sugary mounds that surround me as I gently set down the sled next to my feet. I'm not sure why I'm hesitating here at this hilltop. I've gone sledding every winter since I was a kid, and few slopes ever daunted me. Plus, the hill is short, even if it is pretty steep.

Shielding my eyes from the sun, I survey the park. Dozens upon dozens of excited kids — and adults — are sledding and boarding around me. They zip down effortlessly, shrieking delightedly, then race up to another, higher, hill. Still, I pause. This hill is not like the ones I'm used to back home. Finally, I jump on my sled and begin rocketing down the hill.

Seconds later, almost immediately out of control, I tumble off the sled and watch it nonchalantly continue its downhill journey without me. Then I stand up and begin brushing not snowflakes, but warm sand, from my body.

It's early June and my husband, Ed, and I are sand sledding at Great Sand Dunes National Park in southern Colorado.

The sand dunes here are, rather shockingly, the tallest in all of North America. In this 30-square-mile dune field, five tower at more than 700 feet; the tallest, Star Dune, is 750 feet tall. While a few sand dunes elsewhere in the world rise more than 1,000 feet, Star Dune is one of the tallest on Earth.

Why massive sand dunes in Colorado and not some sandier locale — like a desert, perhaps? It's all about the unique geology and wind patterns found here. In this particular spot, the San Juan and Sangre de Cristo mountains come together to form a little barrier of sorts, with the San Luis Valley at their base. The valley contains sand and sediment from long-evaporated lakes, coupled with sediment blown down from the nearby mountains. The area's predominant southwesterly winds blow the sand and sediment from the valley floor up toward the Sangre de Cristo Mountains in the east. But when storms arise, as they frequently do, their accompanying bluster blows the sand and sediment west, back toward the valley. The result of these battling, sand-filled winds are dunes that rise vertically, composed of sand that is constantly being recycled.

Explorer Zebulon Pike wrote the first known description of the Great Sand Dunes in 1807, calling their appearance "exactly that of the sea in a storm, except as to color … " And indeed, from a distance they appear to be waves furiously lashing against the mountains. But as you move in closer, the dune field's 5 billion cubic meters of sand appear softer, more rounded, more inviting.

Ed is waiting impatiently for his turn on the sled. But I'm discovering it's really hard to walk up the side of a steep sand dune. I begin digging the sled into the shifting, golden grains to give myself some leverage. It doesn't help that the park sits at an elevation of about 8,200 feet, and I come from a city squatting at a mere 984. By the time I reach the top of the dune, I'm puffing as hard as if I'd sprinted up. No wonder local college track runners — and even an Olympian, they say — run up the dunes as part of their workouts.

Before Ed takes his turn, we try to recall the sand-sledding tips we'd gleaned from locals so his trip down can be more successful than mine: Don't pick a hill pockmarked with a lot of footprints or it will be hard to get going. You go faster on wetter, packed sand. Wax your sled in between each run, as the sand quickly abrades it off on one trip down.

Ed waxes the sled, picks a slightly more compacted section of the dune, then flies down without incident.

"Hey, did you end up covered in sand?" he yells up at me, wiping off both forearms. I just smile. Not only is my body still covered in a fine layer of grit, but stray grains are crunching in my mouth.

A half-hour later, the sand quickly warming, we decide to ditch our sand sleds for the day. The sand here can reach a blistering 150 degrees in the summer, we're told, so it's best to sled in the morning. Besides, we need to explore the beach that lies a few paces away. It's Colorado's best, we're told.

Sand Creek hooks around the back, or west end, of the dune field after its journey down the mountainside, largely out of sight of tourists. But Medano Creek proudly dances across the dune field's eastern front, attracting visitors to its ephemeral beach. The creek's peak flow is late May, when the water can swirl as deep as a foot or two.

Strapping on water shoes, we step into the cool, rushing water, which is about ankle-deep. Then we survey the scene. The creek sprawls some 50 feet wide when we visit — its width shrinks to about 20 feet when the water depth is just an inch or two — and is studded with all manner of temporary sandbars: slender, commodious, scallop-edged, ragged.

Families are creating mini-encampments on the largest, sturdiest ones. A typical arrangement is a giant sun umbrella carefully set on its side and surrounded by a colorful mosaic of beach towels, folding chairs, water toys and coolers. One family, more ambitious than most, has hauled a portable grill out to their sandbar; the savory scent of hamburgers grilling wafts over to us, causing my stomach to rumble.

As we stroll through the water, which gets a little deeper and cooler with every step we take upstream and closer to the mountains, we see all manner of people enjoying Colorado's favorite beach: kids swooshing past in brightly colored inner tubes; lovers stealing kisses; elderly folks walking their dogs or grandkids; tatted young adults chucking Frisbees. A father apologizes when his young son careens into us on a purple inner tube, then tells us this is already their third trip to the beach this season. "The creek is different every single day," he says. "So it's always a new experience."

The clusters of people thin out the farther upstream we walk, so now we focus on the water, flowing toward us in smooth, even waves reminiscent of pancake batter as it's ladled onto a hot griddle. Interestingly, the flowage is constantly changing direction and speed. One minute the waves are silky smooth and quietly burbling to our left, the next minute they're roaring as they muscle their way around rocks on our right.

Back in our hotel room, we spread out the park map and plot our adventures for the next few days. In addition to the dunes and beach, the park is noteworthy for its diverse landscapes of grasslands, wetlands, forest, alpine lakes and even tundra. We circle several hiking trails that wind through some of these ecosystems.

We also decide an evening visit is mandatory. On a clear night, Great Sand Dunes is renowned for its stargazing, as it has the necessary trifecta of dry air, little light and a high elevation. Unfortunately, our visit doesn't coincide with a full moon; a stroll atop the dunes under one is said to be magical.

Later, when I crawl into bed, a sprinkling of sand grains falls onto my pillow, remnants of my sand-sledding tumble. As I drift off to sleep, I picture the wind snatching these very grains and whisking them high up to the mountaintop, where they patiently waited until Medano Creek rockets them back down to their home in the expansive dune field. How many times had they made that trip before I carried them away with me?

Melanie Radzicki McManus writes about travel and fitness; she lives in Sun Prairie, Wis.