November 8, 2025 Dr. Ivan Ghezzi, Unidad Ejecutora Chankillo, Casma, Peru: “Astronomy before Chankillo: the development of ideas that led to the world´s most impressive monumental solar calendar.”
The Chankillo Solar Observatory in Casma, Peru, is a 2,300-year-old instrument designed for landscape timekeeping, capable of determining specific dates throughout most of the year with an error margin of just 1-2 days. While similar sites are used to mark key dates such as solstices and equinoxes, Chankillo operates daily at sunrise and sunset, making it a “complete horizon calendar.” The region surrounding Chankillo is characterized by significantly less cloud cover and thus better visibility than much of coastal Peru, which explains in part the title of “the cradle of pre-Inca astronomy.” Despite the wealth of prehistoric sites in the region, many of which represent millennia of monumental construction prior to Chankillo, these sites had not previously been systematically analyzed using modern archaeoastronomical methods. During 2024 and 2025 we have measured specific architectural features at several pre-Hispanic sites across the Casma, Sechín, and Nepeña valleys with the aim of uncovering evidence of the long process of experimentation, learning, design, and knowledge transmission that ultimately led to the creation of the Chankillo Solar Observatory. In this presentation, we shared the results of our archaeoastronomical research, focusing on the use of plazas and platforms—specifically, axes of symmetry and diagonals—as representations of different “axes mundorum” within the pre-Hispanic worldview of the region (3500 BC – 200 BC).
Ivan Ghezzi is an archaeologist from Pontifical Catholic University of Peru, with MPhil and PhD degrees in Archaeology from Yale and specialization in cultural organization´s management from the University of Maryland. Former director of the National Museum of Archaeology, Anthropology and History of Peru, where he started a revitalization, with the opening and renovation of new galleries and temporary exhibits, international exhibitions, and a record increases in visitors, research, inter-institutional collaboration, and donations. He published in Science the discovery of the oldest solar observatory in the Americas at Chankillo, and led the project for its inscription on the UNESCO World Heritage List. He is an associate researcher at the French Institute of Andean Studies and at the Ramon Mugica Scientific Research Station at the University of Piura. He currently directs the Chankillo Executive Unit of the Ministry of Culture of Peru, responsible for the research, conservation, and enhancement of Chankillo. He leads research projects in the fields of dendroarchaeology, paleoclimatology, khipus, remote sensing, archaeogeophysics, and conservation science.