The drive from Taos, in north-central New Mexico, to Chaco Canyon in the northwest corner of the state is so beautiful it could make you cry. There were azure skies, red and gold mountains, giant Wild West cliffs of pastel strata, all the improbable hues you see in New Mexico paintings that make you think the artists must all be constantly imbibing peyote.

But when we drove into the valley that houses Chaco Canyon, the ruins of an ancient city and spiritual center, possibly the most important prehistoric site in America, all beauty vanished. There was nothing but barren, dry, yellow crags and cliffs. As we rattled the 37 miles of washboard dirt road from the last gas station on U.S. 550 to Chaco Canyon National Historic Park, I kept demanding of my three equally stumped teenage children, “Why here? Why did they build it here?”

But to the Anasazi, the “ancient ones” who built and used this place for four centuries, this patch of sandstone was the center of the universe.

Chaco Canyon was built between 800 and 1150 by Puebloan ancestors. Like Stonehenge, it was one of those massive, mysterious monuments to prehistoric ingenuity and spiritual practice that leave a thousand questions. A veritable city, it was remarkably sophisticated, with irrigation systems, aqueducts and a collection of great houses, the two largest with nearly 1,000 rooms each that rose to five stories. The 2-foot thick walls had mud and stone cores veneered with cut slabs and slivers of sandstone in every shade of red, gold and brown. Construction took at least 200 years. Then, about 1300 , the people mysteriously left. Maybe because of drought, or internal factions. Or maybe, some believe, because they had grown too powerful and lost their balance with the natural world.

The heart of Chaco Canyon is a butte that rises like a lonely monument, 380 feet above the desert floor. On this sacred landform, Fajada Butte, ancient astronomers carved a sundial petroglyph to keep the people aligned with the heavens. They carved a pair of spirals and covered them with three sandstone slabs standing at angles. When the sun pierced the gaps between the slabs, daggers of light marked the season. “The Sun Dagger,” as it was named by researcher Anna Sofaer, pierced the center of the spiral at noon on the summer solstice. Another petroglyph appears to be a drawing of the largest great house, Pueblo Bonito. Sunlight pierced the center wall of this great house at the precise moment the sun dagger pierced the spiral atop Fajada Butte.

The Sun Dagger’s been damaged, and tourists are no longer permitted to climb Fajada Butte. But the ruins of the buildings are still there. And it’s still considered a place of incredible spiritual power.

We arrived at the monument in the late afternoon, a little disconcerted by something we’d read in the car. There was a theory that Chaco’s edifices were built by Puebloans enslaved by Mesoamericans who migrated north and bullied thousands of peaceful Southwest people into creating Chaco. They might have used ritual cannibalism to persuade them. Whether it happened that way or not is another unsolved mystery. I choose to go with those who say it didn’t. It makes me like the place a lot more.

We drove to the visitors center and paid $18 for a campsite and the right to stay overnight.

There is only camping at Chaco and precious little of that. One small lot is for RVs, another for tent campers. There’s a clean bathroom with running water but no showers. You must bring your own drinking water and firewood.

We picked a spot close to the bathroom in the shadow of a cliff where boulders the size of minivans were piled up willy nilly. Most of the cliffs here have chunks that have split off and stand like sentries, waiting for rainstorms or time to reduce them to enormous rubble piles. One of these, Threatening Rock, stood over the main great house, Pueblo Bonito. It had weighed more than 30,000 tons and when it finally fell on the ruin in 1941, it took out 30 rooms.

We toured Pueblo Bonito and the other large great house, Chetro Ketl, that evening as the sun set. We were almost completely alone at the site, and the intense stillness of the place and the vastness of the desert made us tour it in near silence, speaking rarely and in low voices, only talking to point out some petroglyph or share a historical fact from the booklet we borrowed at the beginning of the trail. The sun was setting, transforming that hot, yellow place into a beautiful valley of gold, red and purple. The little vegetation looked soft against the hard desert floor. It is unspeakably lonely, but so beautiful in its own way. And I found myself apologizing to the desert and the people, silently.

“I get it now,” I said to no one. Maybe I get it. Maybe their reasons for being here had nothing to do with beauty.

Some people believe the primary purpose of Chaco Canyon was as a center of spiritual practice for all the surrounding tribes. Of the hundreds of rooms, few have hearths, so it seems unlikely that people lived in them. There are many kivas — round rooms under the ground — that are roofless now. Once kivas were underground homes, but when the Pueblo people began to build above ground, the kivas became a place of spiritual practice, a kind of origin place or womb. Some of these kivas could hold hundreds of people. Thousands could have worshipped here all at one time.

My kids and I sat against one of the half-walls, staring at a petroglyph of a man with wild hair under a spiral sun. Someone else was kneeling before him. We tried to imagine what it would be like to live here. It wouldn’t have felt lonely to these people. It was home. It was the center of the universe. They probably knew each undulation of the cliffs. To them, each communal dwelling along the paths held a family member, a friend, a sweetheart.

When we could no longer see the sun behind the cliffs, we drove back to the campsite and made a fire, chopped vegetables and skewered them. We couldn’t find the beef cubes, and we hoped they weren’t still thawing on the kitchen table. We followed the meal with jumbo marshmallows. I had wine.

We slept with the top off the tent, looking at stars that crowded thick in the sky, until we couldn’t keep our eyes open anymore.

Before dawn, my 15-year-old son woke me. We watched the sun rise, a similarly glorious spectacle as the sunset had been. Before leaving, we walked the trail to Wijiji, an outlying home the people might have used to predict the winter solstice using a notch in a distant hill. There were supposed to be some remarkable pictographs.

We trudged the mile and a half trail, but the hotter it got the more demanding I became that the pictographs would open an ancient world for me. Which they didn’t. After staring at a handprint on a wall, a print of someone who’d been dust for a thousand years, we turned back.

I still don’t know why they built it here, though the solar sightlines are remarkable. I don’t know what it was or why they left. But next time I come, I might go off alone for a bit to listen to the silence — and hear what it tells me.