Discovery at Oldest Observatory in the Americas Pushes Back Origins of Peruvian Astronomy

Ancient astronomical structures at Chankillo in Peru's Casma Valley.

November

/ 2025

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Peru's Ministry of Culture has confirmed a groundbreaking discovery that rewrites the history of ancient astronomy in the Americas. Archaeologists working at the Chankillo Archaeoastronomical Complex in the Casma Valley of Ancash region have uncovered architectural structures that predate the famous Chankillo Solar Observatory, which was previously recognized as the oldest solar observatory in the Americas, dating to approximately 250 BC. This remarkable find challenges our understanding of when sophisticated astronomical knowledge first emerged in pre-Hispanic Peru and demonstrates that ancient Andean civilizations possessed complex sky-watching capabilities far earlier than previously believed.

Structures Older Than Known History

The discovery was announced by archaeologist Ivan Ghezzi Solis, director of the Executing Unit 010 Chankillo, following excavations conducted between April and November of this year. According to ANDINA news agency, these newly unearthed structures exhibit clear astronomical orientation and employ different construction techniques than the known observatory, utilizing stone, mud, and adobe materials.

The Ministry of Culture emphasized that:

"this discovery redefines the origins of Andean astronomy and significantly extends the chronology of astronomical development in the region, becoming one of the earliest records of architectural planning oriented toward the movements of the sun in the Americas."

The Chankillo Executive Unit is working to complete excavations and obtain radiocarbon dating to determine the precise age of these ancient structures, which could push back the timeline of astronomical knowledge in the Americas by several centuries or even millennia.

The news excavations with the 13 Towers ridge in the background.

The famous Thirteen Towers solar observatory at Chankillo, now revealed to be younger than newly discovered structures in the area in the foreground. (Ministry of Culture Peru)

Lunar Corridor and Dual Observation System

Beyond the older structures, excavations at Chankillo have revealed another significant finding that expands our understanding of the complex's astronomical functions. Researchers identified a corridor intentionally aligned with the lunar cycle, demonstrating that the site was used for both solar and lunar observations. This corridor faces west toward the fortified temple and aligns precisely with the moon's movements across the sky.

Ghezzi explained that this discovery provides "a richer interpretation of Chankillo as a site for both solar and lunar observations," indicating that the astronomical knowledge possessed by this ancient culture was far more sophisticated and diverse than previously understood. The existence of separate observation points for different celestial bodies suggests a level of astronomical sophistication that rivals other ancient observatories around the world, placing Chankillo among the most important astronomical sites of the ancient world.

Warriors and Astronomers: Elite Knowledge Keepers

Among the most intriguing discoveries at Chankillo was a large ceremonial Patazca-style vessel, approximately one meter in height, found at the entrance to the solar observatory. The vessel features clay figurines depicting warriors in combat positions, arranged in pairs that suggest ritual duels. According to ANDINA, this artifact had been intentionally broken as part of a ceremonial act.

Archaeological excavations revealed ceremonial vessels and warrior figures at the site. (Ministry of Culture Peru)

The placement of this vessel in an exclusive area near the observatory provides compelling evidence that astronomical knowledge was controlled by a warrior elite who combined celestial observation with military leadership. Ghezzi noted that this represents "a wonderful integration: astronomy and combat. These figures were leaders who possessed precise astronomical knowledge and, at the same time, were successful warriors." This fusion of sacred knowledge and martial power reveals much about the social organization of this mysterious pre-Columbian culture, suggesting that control of astronomical information was a source of political authority and religious legitimacy.

Casma Valley: Ancient Astronomical Capital

The Ministry of Culture has declared that these discoveries firmly establish Casma as one of the most important ancient astronomical centers in the world. The Chankillo Archaeoastronomical Complex received UNESCO World Heritage status in 2021, recognizing its significance as the oldest complete solar horizon calendar in the ancient world. The famous Thirteen Towers, which span approximately 300 meters along a ridge, mark the position of the sun's rise and setting points throughout the year with remarkable precision.

The Executing Unit has identified 12 additional astronomical points in the Casma and Nepeña Valleys that will be proposed to UNESCO for recognition as World Heritage sites. These discoveries demonstrate that the region was home to a sustained tradition of astronomical observation spanning potentially thousands of years. Director Ghezzi announced that efforts to extend World Heritage designation to these connected sites could be completed within five to six years, with the first sector of Chankillo opening to the public within two to three years, complete with tourist infrastructure and visitor circuits.

Redrawing the Map of Ancient Astronomy

This discovery adds another layer to Peru's rich tapestry of ancient astronomical sites, which includes the later Inca observatories at Machu Picchu and the Temple of the Sun in Cusco. However, the newly discovered structures at Chankillo predate the Inca civilization by over a millennium, revealing that sophisticated celestial observation was already well-established in the region long before the rise of South America's most famous empire.

The architectural sophistication of these older structures, combined with their precise astronomical alignments, suggests that the unknown culture that built them possessed advanced mathematical and engineering knowledge. The use of multiple construction techniques—stone, mud, and adobe - indicates experimentation and innovation in architectural methods, while the astronomical orientations demonstrate detailed observations of solar and potentially stellar movements over extended periods.

Top image: Ancient astronomical structures at Chankillo in Peru's Casma Valley, revealing early sky-watching traditions in the Americas. Source: Ministry of Culture Peru

By Gary Manners