According to local legend, the ancient Zapotecs built an intricate network of tunnels around a deep earthen cavity in southern Mexico, believing it to be an entrance to the underworld. Later, the story goes, Spanish missionaries sealed off the entrance—which supposedly lay beneath the Church of San Pablo, a Catholic church built in the 16th century.
Now, a new analysis has confirmed that a vast “underground labyrinth” of passageways exists below the site, according to a statement from a team of researchers.
The team found the tunnels beneath the ruins of Mitla, an ancient city in present-day Oaxaca. Mitla served as a religious center for the Zapotecs, a group that emerged from Mexico’s Oaxaca Valley around the sixth century B.C.E. The city’s stunning above-ground mosaics and murals still stand at the site.
In addition to local lore, historical accounts support tales of the tunnels. Writing in 1674, a Dominican chronicler named Francisco Burgoa described an extensive cavity in the earth at Mitla, which a group of Spanish missionaries decided to explore. But when they descended into the maze, “such was the corruption and bad smell, the dampness of the floor, and a cold wind which extinguished the lights, that at the little distance they had already penetrated … they resolved to come out, and ordered this infernal gate to be thoroughly closed with masonry,” wrote Burgoa, per a translation.
The missionaries sealed all entrances to the tunnel network, which the Zapotecs had called Lyobaa, or “place of rest.”
Now, the team working to uncover Mitla’s secrets has adopted the name: Project Lyobaa is a collaboration between the National Autonomous University of Mexico, Mexico’s National Institute of History and Anthropology and the ARX Project.
The researchers created a 3D model of Mitla’s subterranean passageways using a combination of three geophysical scanning technologies—ground penetrating radar, electrical resistivity tomography and seismic noise tomography—all of which left the archaeological site undisturbed.
The scans revealed a “large void located right beneath the main altar” of the church, write the researchers. They also found two more passages located between 5 and 8 meters (about 16 and 26 feet) below the ground, as well as another “geophysical anomaly” north of the church.
“The newly discovered chambers and tunnels directly relate to the ancient Zapotec beliefs and concepts of the underworld and confirm the veracity of the colonial accounts that speak of the elaborate rituals and ceremonies conducted at Mitla in subterranean chambers associated with the cult of the dead and the ancestors,” Marco Vigato, founder of the ARX Project, tells Live Science’s Kristina Killgrove.
He adds that while the researchers expected to find the passageways, they were surprised by their vast scale. “More research is needed to accurately determine the full extent of these subterranean features,” he says.
The team plans to conduct a second round of investigations in September, focusing on Mitla’s other structures. In the meantime, they say that the discoveries they’ve made so far are vital to experts’ understanding of the ancient city.
“These findings will help rewrite the history of the origins of Mitla and its development as an ancient site, as well as providing valuable information for the management and prevention of seismic and geological risk in the area,” the researchers write.
Editor’s note, August 9, 2023: The Church of San Pablo was built in the 16th century, not the 15th century.