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My wife and I have enjoyed hiking in more than a dozen national parks. While some of our favorite hikes have been in and around North Cascades National Park in Washington, we found one of our most unique hiking experiences in south-central Colorado. Great Sand Dunes National Park and Preserve near Alamosa is an awe-inspiring park with the Sangre Cristo Mountains framing the 30-square-mile dune field.

In the summer of 1999, while traveling to visit Mesa Verde National Park and to hike in Arches National Park, we noticed the road sign to Great Sand Dunes and could faintly see the dunes in the distance. Although we didn't have time to drive the 15 or so miles to reach the park, the view intrigued us so much that we decided to return someday to explore it.

In July of 2013 we made it back to Colorado. As we turned off the main road and headed toward the park, the incredible size of the dunes was fascinating. A stop at the visitor center allowed us to gain the necessary information about the park and its origins. It also gave us a spectacular view of High Dune, which rises 700 feet above the valley floor. When we saw visitors climbing to the top of the dune, we could at last comprehend its immense size. Some people were using plastic sleds or pieces of cardboard to slide down the steep slopes of the nearer dunes. We had arrived midafternoon and dark clouds were rolling in. With warnings regarding the possibility of lightning strikes, we decided to come back the next morning.

It rained overnight and the clouds were slowly retreating as we drove to the park the next day. The low angle of the early-morning sun created wonderfully contrasting shadows on the ridges of the dunes.

Upon reaching the parking area, we stepped out into the cool morning air and strapped on our packs with our lunch, snack and plenty of water. As tempting as it was to head straight for the summit of High Dune, we decided to take a longer, more gradual approach. As the sun rose higher, water vapor could be seen rising from the damp sand.

The sand, in places, was as firm as walking on a gravel road and in other places it was like trudging through 10 inches of wet snow.

As the day warmed, we shed layers and found a firm spot to sit while eating a snack. The views of the tree-covered Sangre Cristo Mountains in the distance were in stark contrast to the mostly barren sand dunes on which we were sitting. Eventually, we made it to the summit of High Dune. We took a few photos and kept exploring. By lunchtime, the power of the sun shining on the dunes was quite intense. The temperature of the surface sand in the summer can reach 140 degrees! As the temperature rose, the wind began to pick up the grains of sand, and we could feel the stinging effect on our exposed skin and could feel the grit on our teeth, as well. We decided to wind our way back and resolved to come back the next day.

Our plan for the second day was to reach Star Dune, the park's tallest. It stands 755 feet tall and is at an elevation of about 8,600 feet above sea level. Our meandering early-morning hike to the summit was about 4 miles and we felt like we had the whole park to ourselves.

On the way back, we made our way down to Medano Creek, took off our boots and waded back to the parking area. The river hike allowed us to witness how the unique topography of the valley creates a recycling of the sand. The steep dunes slough off into the creek, which then brings the sand to the upwind side of the park where it dries out and is blown onto the dunes again.

Great Sand Dunes National Park is definitely on our list of places to revisit.

Bruce Fingerson lives in Breckenridge, Minn.