Possible Aztec-era ossuary found beneath Mexico City railway works

Railway crews in Mexico City have uncovered a jumble of human bones that may belong to an Aztec-era ossuary. Archaeologists from Mexico’s National Institute of Anthropology and History (INAH) have identified the remains of at least nine people so far, and two of them show deliberate cranial modification. The date is still uncertain, and that uncertainty is part of what makes the find interesting.

A railway dig in the heart of old Tlatelolco

The discovery came during earthworks for the new Mexico City-Querétaro passenger railway, near the Buenavista terminal. Because Mexican law requires archaeological supervision of major construction, INAH specialists work alongside the builders in what is called salvage archaeology. On 17 September 2026, at a depth of about 1.4 metres, they met the first bones.

The spot lies in the former calpulli of Nonoalco, one of 19 pre-Hispanic neighbourhoods on the island of Tlatelolco. Tlatelolco was the twin city of Tenochtitlan, and it became a major market centre of the Aztec world. A short distance away stands the 16th-century church of San Miguel Nonoalco, which Franciscans from the Convent of Santiago Tlatelolco used as a visiting chapel.

What the team found

The bones did not lie in anatomical order. Skulls, jaws, hip fragments, femurs, ribs and teeth were mixed together, which is why the team provisionally calls the deposit an ossuary, a place where bones were gathered after the bodies had decomposed. So far the archaeologists count nine individuals. They also recovered five additional mandibles and many large bones, such as radii, tibias and pelvic parts, so the final number may be higher.

Two individuals show cranial modification, the shaping of the head in childhood that many Mesoamerican societies practised. The exact style has not been determined yet. Laboratory work will also estimate the age and sex of each person.

Objects found with the bones help place the deposit in time. They include Aztec III pottery, roughly AD 1350 to 1520, mostly domestic plates and cooking pots, along with containers linked to salt extraction from the former Lake Texcoco. The team also found seven miniature spindle whorls, two figurines, four fragments of grinding stones (metates) and obsidian blades, mostly green, which may come from the Sierra de las Navajas in Hidalgo.

Why the date is still open

The pottery points to the late Aztec period, but the mix of pre-Hispanic and colonial material complicates the picture. INAH describes three possible windows: the Late Postclassic (AD 1200 to 1519), the Spanish contact period (1519 to 1535), or the early colonial period. In Mexico City, ossuaries found earlier usually date to the viceregal or contact years, so a deposit that also holds pre-Hispanic material stands out.

One possible explanation is that older graves were disturbed, perhaps by later building, and that people then gathered the bones into a secondary deposit. Researchers say the presence of intact skulls and long bones, rather than small fragments, supports the ossuary reading. They also suggest the people may have been buried elsewhere first and moved later. Nobody has confirmed this yet.

What happens next

The bones and artefacts have gone to INAH project laboratories in Tula de Allende and Tepeji del Río de Ocampo, in Hidalgo. Specialists will clean, restore and study them before they move to permanent storage. Mexico’s Secretary of Culture, Claudia Curiel de Icaza, said the find should deepen understanding of how ancient communities treated and remembered their dead.

Caveats and open questions

Much remains unsettled. The reports we found come from news coverage of the INAH announcement, not from a published excavation report. The date range is wide, the cranial modification is not yet described, and the secondary-burial idea is a working hypothesis. Radiocarbon dates, an age and sex profile, and a closer look at the modified skulls could tell us whether these people lived before the Spanish arrival, during the conquest years, or soon after.

For now, the find is a reminder that modern Mexico City still sits on top of layered, overlapping pasts, and that a new railway line can reopen questions about how people honoured their dead five centuries ago.

Sources

• INAH (Instituto Nacional de Antropología e Historia), announcement as reported on 4 November 2026 (release page not fetched directly)
• HeritageDaily, “Possible Aztec-era ossuary discovered beneath Mexico City”
• La Crónica de Hoy, INAH descubre posible osario prehispánico durante obras del tren México-Querétaro