Great Sand Dunes National Park

The Great Sand Dunes should not be where they are, which is the thrill of them: thirty square miles of Sahara-scale sand pooled improbably against the snowcapped Sangre de Cristo range, the tallest dunes in North America rising about 750 feet from the valley floor. The physics is elegant - winds funnel sand across the San Luis Valley and drop it where the mountains block the way - and the experience is pure play: there are no trails on the sand, so you simply walk up the ridgelines toward High Dune or Star Dune and run, roll or sandboard down. In late spring the park adds its second act, Medano Creek, a shallow sheet of snowmelt that pulses across the sand in rhythmic surge waves and turns the dune base into a mountain beach. After dark, one of the country's certified dark skies takes over.

What you actually see

• The dunefield from High Dune - ridgeline waves of sand against the peaks.
• Medano Creek - the surge-wave beach at the dunes' feet in season.
• Sandboarding runs - rented boards and sleds on the open slopes.
• The night sky - certified dark-sky stargazing over the sand.

When to go

Late May to early June catches Medano Creek at full flow and the valley in spring - the sweet spot. Summer afternoons cook the sand surface hot enough to burn; climb at morning or evening, and expect afternoon thunderstorms.

Honest expectations

Climbing sand is honest labor - the top of Star Dune takes hours, not minutes, and every step slides half back. Rent sandboards outside the park beforehand, carry far more water than feels reasonable, and keep off the dunes when storms build; the ridges are lightning bait.

Nearby

Alamosa, Zapata Falls and the San Luis Valley's wetlands and crane country.