Teotihuacan's 'Pyramid of the Moon' is aligned with the solstice sun, researchers argue

The "Pyramid of the Moon" at Teotihuacán, the site of an ancient city near modern-day Mexico City, is aligned with the sun on the summer and winter solstices, a research team in Mexico says. However, not all experts agree with the assessment.

Teotihuacán flourished between roughly 100 B.C. to A.D. 800 and had a population of around 100,000 people. The "Pyramid of the Moon" was built in stages between roughly A.D. 1 and 350 and is located at the end of the "Causeway of the Dead," a long street that runs through the center of the city. 

The team took a large number of measurements, including information from drone flights, to reveal that the northeast corner of the Pyramid of the Moon aligns with the sun when it rises over the El Xihuingo volcano on the summer solstice, which occurs between June 20 and 21 each year in the Northern Hemisphere, Mexico's National Institute of Anthropology and History (INAH) said in a Spanish-language statement. The researchers also found that the southwest corner of the pyramid aligns with the sun as it sets behind a hill during the winter solstice, which occurs between Dec. 21 and 22 each year. 

The summer-solstice alignment involving the volcano is particularly interesting, the team said, as there is evidence that the people of Teotihuacán used the volcano as an astronomical observatory of sorts. 

"On the slopes of the El Xihuingo volcano is the Xihuingo archaeological site, a place where Petroglyphs known as dotted crosses were created [and] whose function has been proposed as astronomical markers," Aarón González Benítez, an archaeoastronomer at the National School of Anthropology and History in Mexico and a member of the research team, told Live Science in an email. 

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The pyramid's alignment with the solstice sun appears to have affected the orientation of the entire city. "The city of Teotihuacan stands out among other things for its magnificent reticular design, and if the solar orientations of the Pyramid of the Moon determined the orientation of the city, the other monuments that are parallel to this great building would be following and replicating the same canonical orientation," González Benítez said.