When they first came in contact with the Aztecs during the 16th century, Spanish conquistadors were beguiled by the civilization's riches but terrified by its brutality. Located in what is today Mexico City, the capital city of Tenochtitlán was rife with war and bloodshed, which rulers celebrated by building temples to deities like Huitzilopochtli, the Aztec god of the Sun, war, and human sacrifice. According to Spanish accounts, near Tenochtitlán's Templo Mayor ("main temple") was a towering array of human skulls. Now, Reuters reports that archaeologists have discovered a 20-foot edifice made from bones—including those from women and children—that was likely once part of the legendary structure.

Archaeologists discovered the tower's remains on the edge of Templo Mayor. Known as the Huey Tzompantli ("skull rack" in Nahuatl, the Aztec language), the bone tower reportedly once contained tens of thousands of skulls. So far, scientists have discovered more than 650 limestone-encrusted skulls and thousands of bone fragments, and they expect to unearth even more. They were surprised, however, to find that the tower wasn't simply constructed from defeated soldiers' remains: Bones from women and children were also present. While there's evidence that women and children were also sacrificed, their presence in this context was unexpected.

"We were expecting just men, obviously young men, as warriors would be, and the thing about the women and children is that you'd think they wouldn't be going to war," Rodrigo Bolanos, a biological anthropologist affiliated with the project, told Reuters. "Something is happening that we have no record of, and this is really new, a first in the Huey Tzompantli."

The heads were likely publicly displayed before being set in the temple's tower. There, they served as an ominous reminder of the Aztec's might—that is, until Hernán Cortés and his soldiers captured and destroyed Tenochtitlán in 1521.

[h/t Reuters]