Archaeologists Reveal Ancient Solar Observatory in Peru

Article ID: 527606

Released: 26-Feb-2007 12:00 AM EST

Source Newsroom: Earthwatch Institute

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  • Credit: Ivan Ghezzi

    The 13 Towers stand out among the ruins of Chankillo in Peru's coastal desert. Earthwatch-supported archaeologist Ivan Ghezzi (Pontificia Universidad Catolica del Peru) has identified this ancient construction as an pre-Inca solar calendar.

  • Credit: Ivan Ghezzi

    Earthwatch volunteers take measurements at a pre-Inca site in Peru's coastal desert. For three years, Earthwatch teams helped Ivan Ghezzi excavate and survey the ceremonial complex of Chankillo, including the solar calendar called the 13 Towers.

  • Credit: Ivan Ghezzi

    Earthwatch volunteers help Ivan Ghezzi excavate another pre-Inca site near Chankillo. In addition to mapping Chankillo's 13 towers, volunteers excavated associated buildings and took tree ring samples from wooden lintels that helped date the site.

  • Credit: Ivan Ghezzi

    Sunset over the 13 Towers of Chankillo on the June solstice demonstrates the purpose of the structures. Earthwatch-supported archaeologist Ivan Ghezzi has shown that this solar calendar predates Inca sun cults by nearly 2,000 years.

Newswise — Solar calendars and sun cults were an important part of indigenous American culture, from the Hopi to the Inca sun temple in Cusco, Peru. The latest issue of Science features a new discovery at Chankillo, in the Casma Valley of Peru's coastal desert, pushing sun cults in the region back nearly 2,000 years.

A line of structures known as the 13 towers run north-south along the ridge of a low hill at Chankillo, a ceremonial center dating back to the fourth century B.C. From evident observation points on either side, the towers form a "toothed" horizon that spans the annual rising and setting arcs of the sun, indicating their use in solar observations.

"Chankillo is arguably the oldest solar calendar that can be identified as such with confidence within the Americas," said Ivan Ghezzi (Pontificia Universidad Catolica del Peru), who coauthored the Science paper with Clive Ruggles (University of Leicester).

Starting in 2000, Earthwatch volunteer teams assisted Ghezzi at Chankillo for three years, conducting excavations that supported this new revelation about the site's importance in ancient sun cults. They assisted in mapping the 13 towers, recording their alignments, and excavating the "solar observatory" to the west. Earthwatch volunteers also took tree ring samples from well-preserved wooden lintels that helped date the site. "Many indigenous American sites have been found to contain one or a few putative solar orientations," continued Ghezzi. "Chankillo, in contrast, provides a complete set of horizon markers and two unique and indisputable observation points."

Excavation of ancient buildings to the west of the towers revealed one corridor that was clearly an observation point for watching the sun rise over the toothed horizon. The end of the corridor was littered with offerings of pottery, shell, and stone artifacts not found elsewhere nearby, indicating significant rituals associated with solar observations. A building to the east is in the exact mirror position of the western observation point, and is lined up to view the sunsets over the 13 towers.

The gaps between the towers are wide enough for just one or two sunrises to be observed in each. The regularity of the gaps suggests that the year was divided into regular intervals.

Plazas near the 13 towers apparently provided a setting for people participating in public rituals and feasts directly linked to solar observations. However, the observation points themselves appear to have been highly restricted to individuals with special status. This, along with ceramic warrior figurines found at the site, suggest the authority of an elite few. As with the Inca empire, two millennia later, sun worship and cosmology may have helped legitimize that authority.

"Chankillo was built approximately 1700 years before the Incas began their expansion," said Ghezzi. "Although there is obviously no direct culture-historical relationship between the 13 Towers of Chankillo and the sun pillars of Cuzco, they are analogous as horizon markers for calendrical purposes. Now we know these practices are quite a bit older, and were highly developed by Chankillo's time."

Earthwatch Institute is a global volunteer organization that supports scientific research by offering members of the public unique opportunities to work alongside leading field scientists and researchers. Founded in 1971, Earthwatch's mission is to engage people worldwide in scientific field research and education to promote the understanding and action necessary for a sustainable environment. Please include the web site for Earthwatch Institute ( in any story based on this release so that your readers can find out how to join scientific expeditions.

This research will appear in the 2 March, 2007, issue of the journal Science, published by the AAAS, the world's largest general scientific organization. See, and also

To learn about a current Earthwatch project exploring Pre-Inca Peru, Archaeology of Peru's Wari Empire, go to For a related news release go to


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