Ruin Complex in Peru Believed to be the Oldest American Solar Observatory

The fortified stone temple at Chankillo. [Image courtesy of National Aerial Service, Peru]

The Thirteen Towers of Chankillo, a series of 2,300-year-old towers spread over 300 meters on a hilltop in Peru's Casma-Sechin River Basin, form the oldest solar observatory in the Americas, according to new research in the 2 March issue of Science

The towers, part of a larger set of surrounding ruins located 400 kilometers north of Lima, mark the annual rising and setting arcs of the sun and serve as a calendar accurate to within a few days.

By standing in two viewpoints positioned around the walls, scientists says, an observer is able to establish the beginning and midpoint of the solstice year by documenting the sun's position in reference to the gaps between the towers.

In their paper, researchers Ivan Ghezzi, archaeologist at the Pontificia Universidad Catolica del Peru in Lima, and Clive Ruggles, professor of archaeoastronomy at the University of Leicester in Leister in the United Kingdom, contend that the towers move back the date at which civilizations began observing and measuring the sun.

"The Chankillo towers provide evidence of early solar horizon observations . . . preceding [Incan observation towers] by almost two millennia," the researchers wrote.

The Thirteen Towers, views from the fortified temple. [Image courtesy of Ivan Ghezzi]

While earlier research documenting the ruins' thick walls, gates, and strategic location led some to believe the complex was a fortress, archaeological excavations revealing pottery and shells, along with the complex's lack of water resources, suggested that its purpose was ceremonial in addition to scientific.

Because sun worship could have helped to legitimize the authority of an elite class, the authors believe that "the towers were not a simple instrument for solar observation but the monumental expression of existing—and therefore by implication even older—knowledge."

Evelyn Brown and Benjamin Somers

1 March 2007