Ancient Equinox Alignments Found in Cuicuilco, Mexico

ENAH buildings orient toward sunrise implicit Papayo Hill astatine equinoctial dawn. Credit: INAH Mexico

New probe suggests that equinox alignments shaped the municipality plan of Cuicuilco, 1 of the earliest settlements successful what is present confederate Mexico City. Researchers from the National Institute of Anthropology and History (INAH) accidental the site’s layout was oriented toward the rising prima implicit Cerro Papayo, a elevation to the east, during equinoctial mornings.

Archaeoastronomer Aarón Uriel González Benítez of the Astronomical Society of Iztapalapa led the survey done the Department of Cultural Dissemination of the National School of Anthropology and History (ENAH).

He recovered that the sun’s evident way implicit the skyline aligns with 2 periods of the pre-Hispanic Cempohuallapohualli calendar.

These periods, known arsenic tozoztontli and teotleco, correspond to the outpouring equinox astir March 24 and the autumn equinox astir September 20.

Cuicuilco’s pre-Hispanic calendar and its equinox types

González Benítez noted that the globally recognized outpouring equinox falls connected March 20 oregon 21, but past societies observed antithetic types. The “middle” equinox marks the midpoint betwixt solstices. The “cultural” equinox, by contrast, is defined by a group’s ain calendar traditions based connected the sun’s evident question crossed the horizon.

The main buildings of the ENAH (National School of Anthropology and History) are oriented towards the sunrise implicit Papayo Hill connected the equinoxes. Courtesy: Aarón González. pic.twitter.com/yIwOQdhhm8

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Buildings VI and VIII astatine Cuicuilco B look straight toward Cerro Papayo. Their quadrate geometry aligns with the rising prima connected the projected taste equinox dates of March 23 and 24. Academic sources person agelong identified that elevation arsenic a cardinal scenery diagnostic tied to star reflection astatine Cuicuilco A.

González Benítez explained that successful pre-Hispanic culture, municipality centers served arsenic the axis of the satellite for their communities. Architecture, earthy landscape, and star question worked unneurotic to people the astir important moments of the taste calendar.

Ancient equinox alignments echoed crossed modern Mexico

The signifier extends beyond the past ruins. Buildings connected the ENAH campus, including its main building, annex, Guillermo Bonfil Batalla Library, and Research Tower, look betwixt 89 and 90 degrees azimuthal east. The thoroughfare grid of the neighboring Isidro Fabela territory follows the aforesaid direction.

Researchers confirmed this overlap firsthand connected March 23, 2026. González Benítez described the similarity betwixt past and modern orientations arsenic an bonzer coincidence, 1 that lends the schoolhouse an astronomical magnitude it had not antecedently claimed.

José Manuel Castillo Hernández, caput of ENAH’s Department of Cultural Dissemination, said the findings transportation existent acquisition value. He argued the find keeps section astronomical traditions live and deepens the enslaved betwixt the schoolhouse and the archaeological portion beside it.

These past equinox alignments crossed Mexico, helium added, besides connection a meaningful mode to bring pre-Hispanic cognition straight into the classroom.