The biggest sand dunes in the United States are not on the coasts. They aren’t even on the shores of the Great Lakes. They are landlocked in the armpit of the Colorado Rockies.

It’s just one of those interesting things you probably don’t know until you decide to actually turn off the highway and check out a park site. All along the road you see mountains, mountains and more mountains, but just before they swing out ahead of you (going east, anyway), a side road shoots northward and takes you to the dunes. Even then the sand doesn’t appear until you’re close, tucked as it is among the foothills.

Dwarfed they may be by the Rockies, but get up to them and, at 750-feet tall, the dunes stand out pretty distinctly huge. Sunlight makes them glow, but they are ribbed like a dripping cake, the colors shifting from tan to brown to red; cloud shadows fly across them and make fleeting purple bruises.

This is the desert you dream of as a child: Endless sand, without tuft or cactus. Camel country in a country with no camels.

I am reluctant to climb into the dunes. Memories of struggling up the slopes of Indiana Dunes National Seashore in the Midwest trouble me, and this place is much farther from civilization. At the visitors’ center are wheelchairs with massive dune-buggy wheels, but since I am not ready (mentally) for that alternative, out I go, with a bottle of water in one hand and my trusty alpenstock in the other.

Surprisingly, the quality of the sand here seems much more dense and moist than what I trod at the Great Lakes. It shifts, but not endlessly. The guy I’m traveling with is panting as much as I am, and though it’s no comfort to him, I feel better about our progress. Around us, of course, younger people speed up the hill, toting cardboard panels for a sled ride down the slopes. I envy them, but more for the cardboard than their energy.

As they slide down, we keep trudging upward.

Get high enough and the dunes becomes moon-like. Our shoes make shallow prints in earth that is more like dust, and I am reminded of those famous photos from Apollo 11. Stopping to take a drink, I feel like I’ve come a long way, and the weirdness of the place comes back to me.

Sand above me, sand before me, a green valley below and, out beyond, rocks rising up into snow.

I love these places where everything seems out of place. That they are not – that they are exactly what they are supposed to be – makes almost anything seem possible.