Ancient Sun Observatory
Ancient astronomical sites are spread across the earth, and have been fascinating people for millennia, the most famous being the Stone Henge. What is less known is that the Americas also have one. It is called the Chankillo Archaeoastronomical Complex and it dates from between 500-200 BC. Located in the north-central coast of Peru in the Casma Valley, it comprises a set of constructions and natural features that together functioned as a calendar, using the Sun to define important dates through the year.
The Casma Valley has historically been an oasis for human settlement in an otherwise inhospitable environment, where the Casma-Sechin river basin flows down the Andes Mountain range, crossing one the of the driest deserts in the world. Even in this harsh environment, the area has many locations that have been under long human occupation, for at least 4,500 years. Among these, the Chankillo Complex is 2,300 years old – a site where excavations took place between 2000 and 2003 to reveal these fantastic structures.
Chankillo Archaeoastronomical Complex
Since 2021, it has been a UNESCO World Heritage site, according to which, it “includes a triple-walled hilltop complex, known as the Fortified Temple, two building complexes called Observatory and Administrative Centre, a line of 13 cuboidal towers stretching along the ridge of a hill, and the Cerro Mucho Malo that complements the Thirteen Towers as a natural marker. The ceremonial centre was probably dedicated to a solar cult, and the presence of an observation point on either side of the north-south line of the Thirteen Towers allows the observation both of the solar rising and setting points throughout the whole year. The site shows great innovation by using the solar cycle and an artificial horizon to mark the solstices, the equinoxes, and every other date within the year with a precision of 1-2 days. It is thus a testimony of the culmination of a long historical evolution of astronomical practices in the Casma Valley”.
The Portal to the Heritage of Astronomy says that “only the ceremonial structures that survive, generally using spaces that would not compromise maximum use of the riverside land for agriculture. The less robust residential sites and cemeteries, perhaps more closely associated with the cultivation zone along the rivers, are no longer visible”.
According to archaeologists, during the time of Chankillo’s occupation the structures would have been coloured tan, yellow, ochre, or white, and sometimes covered with relief, graffiti or fingerprints.
The famous 13 Towers of Chankillo run north to south, spreading across 300 meters (or 980 feet), forming a row of teeth-like protrusions and all together were used as a solar observatory.
“Chankillo Archaeoastronomical Complex is an outstanding example of ancient landscape timekeeping, a practice of ancient civilizations worldwide, which used visible natural or cultural features. Incorporated in the Thirteen Towers, it permitted the time of year to be accurately determined not just on one date but throughout the seasonal year. Unlike architectural alignments upon a single astronomical target found at many ancient sites around the world, the line of towers spans the entire annual solar rising and setting arcs as viewed, respectively, from two distinct observation points, one of which is still clearly visible above ground. The astronomical facilities at Chankillo represent a masterpiece of human creative genius,” reads the UNESCO description.
Over the course of the year, as the Sun rises in the east, it can be seen along the ridge of the 13 Towers. Sunrise moves from one ridge to the other as the year passes. The placement of the Towers is so perfect that an observer can tell what time of year it is (within two to three days) just by looking at the sunrise or sunset if they stand at a particular position. At the time of the summer solstice, sunrise can be observed to the right of the right tower, while during the winter solstice it can be seen to the left of the left tower. The September equinox can be observed when the Sun sets between the sixth and seventh towers.
According to the Portal to the Heritage of Astronomy, “it was devoted to regulating seasonal ritual events, such as religious festivals, solar worship, and the staging of ritual or real battles, maintaining a ceremonial calendar through solar observations.”
Not much is known about the ancient civilisation that designed and constructed this awe-inspiring observatory, except that it would have been one of the oldest ones in the Americas, predating the Incas by more than 1,000 years. And just like the Incas, they probably worshipped the Sun as a god. “The solar observatory at Chankillo is thus a testimony of the culmination of a long historical evolution of astronomical practices in the Casma Valley”, says UNESCO. The civilisation is now known as the Casma-Sechin culture due to its location between the Casma and Sechin rivers.
The Chankillo Archaeoastromical Complex was occupied for a mere few hundred years, after which it was abandoned for unknown reasons.
“Ancient Andean peoples often structured their actions within a particular view and understanding of the landscape, including the sky. The solar observation device at Chankillo reveals a great deal about the ways in which in this part of the world—people before the advent of written records—perceived, understood, and attempted to order and control the world they inhabited through astronomy. Therefore, Chankillo and its astronomical installations bear unique and exceptional testimony to a cultural tradition that has disappeared”, reads the description in Heritage of Astronomy.
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