Chimney Rock, Colorado

Chimney Rock, Ancient Site And Observatory

Another Chacoan outlier,Chimney Rock archaeological site, is one of the most remarkable ancient site in the Four Corners area. It lies on the southern edge of the San Juan Mountains, in Colorado. At over 7,000 feet, it lies at the highest elevation of all known outliers.

Centered around two natural stone pillars, this site has a special connection to the moon cycle. In this way, it also seems to have acted as an observatory. Of the moon, at least.

Chimney Rock and the Major Lunar Standstill

Chimney Rock Colorado 1

Specifically, during the winter solstice of each Major Lunar Standstill, the moon seems to be rising between the two pillars, Chimney Rock and Companion Rock as viewed from the Great House Pueblo.

Dr. J. McKim Malville, professor of Astrophysics at the University of Colorado at Boulder, demonstrated this fact in 1987. He also suggested that the people of Chimney Rock were aware of these events, and built the Great House Pueblo to mark the beautiful and rare event.

In A.D. 1093, a prevalent construction date for the Great House, the moon was rising between the rocks.

From 2004 through 2007, as seen from the recently removed Forest Service Fire Lookout Tower, the MLS moon rose periodically between the two stone pillars that give the site its name. This spectacular sight, which occurs every 18.6 years, is believed to have influenced construction of the Chacoan-style Great House atop Chimney Rock’s high mesa. Whether coincidence or planned, the Great House Pueblo is a natural observatory for the MLS.

What is a Major Lunar Standstill?

The Major Lunar Standstill, or MLS for short (living in the US, I am getting used to the abbreviations, though I don’t appreciate them), happens every 18.6 years, and it means that for three consecutive years the moon rises in the same spot.

To understand it, you need to remember that the moon’s orbit around the Earth wobbles. This movement causes the moon to rise at different points on the horizon over the years. The full cycle of wobbling takes 18.6 years. At each end of each 18.6-year period, this movement seems to stop for about three years. This means that for there years after each 18.6-year period the moon rises at the same point on the horizon. Then it starts moving back toward the opposite end of the swing.

MLS or the Major Lunar Standstill denotes this pause.

Right now, we are actually in a MLS, that started in 2021.

In Chimney Rock National Monument, this spot happens to be between the two stone pillars, when viewed from a certain place nearby. And this is the place that the Ancestral Puebloans from Chaco (or with connections to Chaco), built their village. Actually, both a ceremonial site and village.

Chimney Rock as the place to view the MLS

The stone pillars as seen from the Chimney Rock kiva
The stone pillars as seen from the Chimney Rock kiva

Archaeoastronomers helped establish the age of the structures in the Chimney Rock Great House, and compere them with the MLS dates. They found that some wood samples date from 1076, a year MLS was visible. Others date from 1093-1094, another MLS date, when they possibly added more elaborate structures.

Though it might be a coincidence, all evidence points to the fact that the Chacoans built this site here, to view the moon rising through the pillars during MLS dates. How did they find this place is anyone’s guess. At least I haven’t read or heard any explanations about that.

We know that Chacoans traveled, since we know of many outlier communities they established. Most likely they happened to be in the exact spot where, looking at the two natural towers, they saw the moon rise between them. That must have prompted them to build a ceremonial site or observatory, along with the village.

The Ancient Village

The site preserves 200 ancient homes and ceremonial buildings and covers seven square miles.

The most elaborate structures, a Great Kiva and a Chacoan-style Great House Pueblo, are at the highest elevation, and offer a perfect view of Chimney Rock. The structures are obviously like Chaco; the same patterns, the same construction, same design.

Besides being the ceremonial site, this was home to people higher in the village hierarchy.

Just below, another Great House is similar in construction and purpose, though it has no direct view of the rocks.

And then there is the the place where most people lived, the real village, a bit lower on the mountain. You’ll find a paved trail leading to and through it. This is where you’ll see several pit houses, and a multi-purpose family dwelling.

Visiting the Site

It was a cloudy morning when we drove through Colorado’s San Juan Mountains from Durango towards Pagosa Springs. Even through the cloud-cover, we noticed the two rock spires, Chimney Rock and Companion Rock from the road.

View of Chimney Rock from the road
View of Chimney Rock from the road

We’ll stop there, we decided, if it’s open, and drive as close to it as possible. We didn’t know we could actually drive up for a close-up view. Still, we thought we’d at least stop at the site’s Visitor Center. So, we saw the sign for Chimney Rock National Monument, we turned onto the dirt road leading to it.

At the Visitor Center, the rangers had an information desk set up outside, near the parking lot.

“You can drive up to the site, just register here,” one of them said. “I would suggest you do that now, because it looks stormy. Visit the highest site first, near the rocks, then if it doesn’t start raining, you can also visit the pit houses in the lower site. Stop at the Visitor Center on your way back.”

Dark storm-clouds were gathering overhead, so we we followed the ranger’s suggestion, and drove up on the mountain.

After several twists and turns on the dirt road, we arrived. By then, the clouds decide to move away, so it looked like we would have more time than we hoped for.

We hiked up the short, but steep trail to the Great House Pueblo and Chimney Rock.

A Gorgeous Setting For An Ancient Village

The view from the Chimney Rock Great House site
The view from the Chimney Rock Great House site

It was the perfect setting for this ancient village. In every direction, they had far-reaching views of the pine-filled mountains and valleys. At the top, we had 360-degree views of Colorado and New Mexico.

In fact, as we found out, from way up here, at around 7,000 feet elevation, the Ancestral Puebloans could communicated with Chaco, about 200 miles away. Not directly, but using a smaller site in between, but still… it’s a long way to see.

The cloud cover kept it more pleasant to explore the site, while still allowing us visibility miles and miles away, through the dramatic landscape of the San Juan Mountains and far beyond.

At The Great House Pueblo Site

Interconnected rooms and kiva at the Chimney Rock Great House.
Originally a two-story structure, the Chimney Rock Great House includes interconnected rooms along with a kiva.

The construction of the site up here reminded us of Chaco’s Pueblo Bonito, with the Great kiva surrounded by several rooms. On top of this mountain, the structure is much smaller, but still the same style.

Originally a two-story structure, this Chacoan Great House stood on the highest spot on this mountain where it was possible to build.

After spending enough time up on top of the world, while other visitors came and went, we descended to the parking lot. From there, we took the paved, interpretive trail through the “real” village, where most people lived.

The Ancient Village Site Below

Remains of a Chimney Rock pit house
Remains of a Chimney Rock pit house

We walked by several pit houses, some larger than others. Contrary to most pit houses we’ve seen in the desert and in the Four Corners area, these were not built partially underground. And they were round, instead of the square shaped I was used to.

Here, the pit houses had a lower wall, made of rocks and mud mortar, and the upper walls were made of wood poles covered with a different mortar. The roof was supported by log posts, and it offered the only entryway through ladders. They also had a ventilation tunnel on the south wall.

The Visitor Center And Museum

Device explaining the lunar orbit and MLS in the Museum
Device explaining the lunar orbit and MLS in the Museum

After spending time in both sites, and enjoying the views and gorgeous cloudy weather, we drove back to the Visitor Center.

The museum here is one of the best ones at any archaeological site. Though it has some pottery exhibits, most of it deals with archaeoastronomy.


We lingered some more, and noticed a short nature trail behind the Visitor Center. As soon as we set off on it, we felt a few rain drops. Eventually, it did rain at Chimney Rock. But only after we finished our visit, and explored everything on site.


  1. What is Chimney Rock Pueblo?

    Chimney Rock Pueblo or archaeological site is an Ancestral Puebloan (also known as Anasazi) site, with close ties to Chaco. Called a Chacoan outlier, it is one of the sites influenced by the larger site. It is the outlier at the highest elevation, most likely built there to observe a celestial event as seen through the two natural rocks pillars.

  2. What celestial event is connected to Chimney Rock?

    The Major Lunar Standstill or MLS, a phenomenon appearing every 18.6-years, is visible from the Chimney Rock site. During the MLS, the moon seems to be rising between the two natural rock pillars as seen from the ancient pueblo. This is especially obvious for the full moon around the winter solstice. Archaeoastronomers believe that the Ancestral Puebloans built this village here after they noticed this phenomenon.

  3. Where is Chimney Rock National Monument?

    Chimney Rock, incorporated into a National monument, is in Colorado, in the San Juan Mountains, between Durango and Pagosa Springs.

Chimney Rock. View of the rocks from the Great House
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