Chaco Canyon is a shallow, 10-mile gorge slashed into the earth in the northwest corner of modern-day New Mexico. At an elevation of 6,200 feet (1,900 meters), its weather is harsh, with blazing summer heat and bitterly cold winters. Still, people have been calling this place home for thousands of years: evidence of nomadic civilizations date back to 2900 B.C., and the first farmers were believed to have settled there around A.D. 200.

But it was A.D. 850 when things really got going: the Chacoan people laid more than 120 miles (200 km) of road and erected massive stone and wood buildings—we're talking as much as five stories tall with up to 700 rooms. But it wasn't the size that was the most interesting part about these structures; it was their position. They were precisely aligned to astronomical "landmarks" like the celestial meridian—that is, the imaginary line in the sky that connects the North and South poles—along with the solar and lunar azimuth (the paths in the sky that the sun and moon follow, respectively). These alignments are important to astronomers because they make it easier to keep track of where things are in the sky.

There was plenty of other evidence pointing to the Chacoans' impressive knowledge of astronomy, too. Carvings in the ground known as petroglyphs marked the cycles of the sun and moon, the most famous of which is known as the Sun Dagger: a spiral design believed to track the moon's 18.6-year cycle. Those grand buildings are also strangely over-embellished, which some scholars think was an expression of Chacoan "concepts of the cosmos."

It's clear that the stars were important to the Chacoans, and why wouldn't they be? That impossibly huge, incredibly dark sky just begs people to look up. Thanks to recent conservation efforts, modern society hasn't diminished its beauty: more than 99 percent of Chaco Culture National State Park has been designated as a "natural darkness zone," where there's no permanent outdoor lighting. That led to its certification as an International Dark Sky Park by the International Dark-Sky Association—a designation given to areas "possessing an exceptional or distinguished quality of starry nights" that specifically protect them for the benefit of research, education, culture, and public enjoyment.

Until 2016, it was also the only National Park with its own astronomical observatory. Built in 1998, the Chaco Observatory is used mostly for science outreach. Visitors can peer through the telescopes, participate in astronomy programs, and learn about the way ancient cultures in the area thought about the cosmos. The technology might be more advanced, but in the end, modern fans of astronomy are no different than the ancient Chacoans. We're all fascinated by the stars above us.

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