Ancient Astronomical Structure Uncovered Near Chankillo, Reshaping Peruvian Chronology

Archaeological investigations in Peru's Áncash region, specifically within the Casma River valley, have uncovered a monumental structure that predates the established Chankillo Solar Observatory. This significant finding is fundamentally altering scholarly perceptions regarding the genesis of organized astronomical science in the Americas. The Chankillo Archaeoastronomical Complex, which received UNESCO World Heritage Site status in 2021, was previously recognized for its iconic alignment of 13 towers, constructed around 250 BCE. This newly identified architectural layer pushes the chronology of sophisticated celestial observation in the region further into antiquity.

The Peruvian Ministry of Culture officially confirmed the excavation in late November 2025, stating that the newly found edifice clearly demonstrates solar orientation and was intentionally engineered for tracking celestial trajectories. Archaeologist Ivan Ghezzi Solis, director of Executing Unit 010 Chankillo, noted that initial assessments of the stratigraphy and construction components—including stone, mud, and adobe—indicate the structure is considerably more ancient than the Solar Observatory. Formal radiocarbon dating is currently being pursued to establish a definitive timeline for this precursor construction.

Further exploration within the complex revealed an additional, intricate feature: a corridor specifically engineered for alignment with the lunar cycle. This passage is oriented westward, facing the fortified temple structure, confirming that the ancient society at this location monitored both the sun’s predictable annual path and the moon’s more complex, recurring rhythms. This dual-tracking capability suggests the astronomical expertise of this civilization was more diverse and advanced than previously accounted for in Andean archaeological models. The Casma–Sechín culture, associated with this area, is already known for some of the earliest monumental architecture in the Americas, dating between approximately 2000 and 1000 BC.

Near the observatory, investigators unearthed a substantial ceremonial vessel of the Patazca style, standing nearly one meter high and adorned with clay figures depicting warriors in combat poses. Its location within a restricted zone implies that the ruling elites who commanded military strength also held proprietary control over specialized astronomical knowledge, thereby reinforcing the existing social hierarchy. Ghezzi characterized this as an integration of "astronomy and combat," pointing to leaders who were both successful warriors and possessors of precise celestial data.

The cumulative discoveries firmly establish the Casma Valley as "one of the most important ancestral astronomical centers in the world," according to the Ministry of Culture, placing it alongside major Peruvian heritage sites like Nazca and Machu Picchu. Conservation efforts are actively progressing on the existing Thirteen Towers, which span approximately 300 meters along the ridge. The Executing Unit plans to increase public access to this section of the complex within the next two to three years, while also identifying twelve additional astronomical points across the Casma and Nepeña Valleys slated for proposal to UNESCO for World Heritage designation within the next five to six years.