In Mexico, while constructing a new railway line, a chilling monument emerged from the earth. Just a few meters below the surface, archaeologists conducting rescue operations before the start of construction uncovered a momoztli—the Nahuatl term for a small ritual altar where communities left offerings.
However, this particular altar, discovered in the former Toltec capital of Tula—known in Nahuatl as Tollan—and tentatively dated to the Tollan phase of the city between 950 and 1100 AD, delivered a grim surprise to researchers.
The city of Tula flourished after the decline of the sprawling metropolis of Teotihuacan to the southeast and before the rise of the Aztec Empire.
It became the heart of the Toltec civilization, whose architecture, religion, and artistic traditions influenced later cultures in central Mexico. By the time the Aztecs arrived centuries later, they revered the Toltecs as legendary builders and craftsmen.
Alongside various obsidian blades and ceramic vessels, the archaeological team unearthed human remains.
As the excavation continued, the scale of the find became increasingly clear. Four skulls were discovered around the altar, one of which was still attached to several cervical vertebrae, prompting the archaeological team to investigate whether this individual had been decapitated.
If the head had separated naturally after burial, it would typically detach only after the soft tissues holding it to the neck had decomposed. Instead, the skull appeared to have been removed while these tissues were still intact, suggesting it was deliberately severed from the body.
But this may not even be the most significant part of the story.
Researchers also uncovered walls and floors indicating that the altar was once situated in the center of a courtyard, possibly within an elite residence or administrative complex.
“We suspect these were either rooms, part of an elite compound, or remnants of palaces that could have existed at this site, associated with higher-ranking groups,” explained archaeologist Víctor Francisco Heredia Guillén from Mexico’s National Institute of Anthropology and History (INAH). “We know that the outskirts of Tula housed neighborhoods populated by upper and middle classes, while commoners lived much farther away.”
The altar itself is roughly square, measuring one meter per side, and consists of three layers of stone: a base of quarried stone, possibly andesite; a middle layer of modular blocks carved from the same stone; and a top layer of river stones and basalt.
At the altar’s base, two skulls were found: one facing upward and the other oriented southwest. The remaining two skulls, along with what are believed to be several human femurs and other artifacts, were retrieved from beneath a compacted layer of plaster in front of the altar.
Researchers say the remains may represent evidence of ritual sacrifice and will examine the bones for such indicators.
“Although metals were already being worked during the Postclassic period, we know that decapitation here was still performed using obsidian or flint knives, which leave cut marks on the bones,” said Heredia Guillén.
Momoztli were small ceremonial altars where offerings were made to deities or ancestors. Archaeologists frequently find ceramics, obsidian blades, and other ritual items around them, as well as human remains.
The discovery was made during archaeological work conducted ahead of the construction of a new passenger railway line between Mexico City and Querétaro. Such excavations are designed to investigate, document, and recover archaeological remains before construction begins.
For now, the altar is being meticulously documented through photographs, drone footage, and detailed sketches, while archaeologists decide on the best way to preserve it.
Other artifacts found at the excavation site have been transferred to laboratories for further study, the researchers reported.
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