Mexico’s Ancient Inhabitants Moved Land and Bent Rivers to Build Teotihuacán

Ancient engineers went to extraordinary lengths to align Teotihuacán, a major pre-Aztec city in what is now central Mexico, with the cosmos, a new study finds. What’s more, reports Isaac Schultz for Gizmodo, these centuries-old interventions continue to influence modern urban development in the same eight-square-mile area.

Today a major tourist destination about 25 miles northeast of Mexico City, Teotihuacán was founded as early as 400 B.C.E. but only as emerged the region’s most powerful city after 100 C.E., wrote Matthew Shaer for Smithsonian magazine in 2016. At its heyday around 500 C.E., some 125,000 to 200,000 people lived in the city, with families dwelling in sprawling apartment complexes decorated with colorful, intricate murals, per Encyclopedia Britannica.

A trading hub for merchants across Mesoamerica, the inner city boasted wide streets and enormous pyramids, some of which—including the famed Pyramids of the Sun and the Moon—still stand today. Though the civilization collapsed abruptly around 600 C.E., much of its architecture endured. Centuries later, around the 1300s, the ruins of the great city so impressed the Aztecs that they gave the site its Nahuatl name, which roughly translates to “the place where the gods were created.”

Published in the journal PLOS One, the new study helps quantify the centuries of human labor that went into shaping Teotihuacán’s iconic structures. Using LiDAR (light detection and ranging) scanning technology, on-the-ground surveys, and other aerial imaging methods, archaeologists led by Nawa Sugiyama of the University of California, Riverside, mapped how workers displaced huge amounts of soil and bedrock and redirected two major rivers to construct the city.

“People have been extensively modifying the built environment for millennia, and in urban contexts, like the ancient city of Teotihuacán, they were changing courses of rivers, altering the topography, and affecting the agricultural potential for the area,” Sugiyama tells Gizmodo.

In recent decades, archaeologists have touted LiDAR technology as revolutionary for the field. By bouncing lasers against the landscape and measuring how long they take to return to their source, researchers have been able to reveal underground structures otherwise “hidden in plain sight,” says Sugiyama in a statement.

The scholars succeeded in using LiDAR to show how ancient city planners rerouted the San Juan and San Lorenzo Rivers to align with points of astronomical significance as they passed through the city center. The team also identified 298 underground features and 5,795 humanmade terraces that once stood in the ancient city but had not previously been recorded.

Sugiyama and her colleagues determined that that Teotihuacán’s builders quarried enormous amounts of material, often working down to—and even mining—the bedrock. In one area of the city known as the Plaza of the Columns Complex, the team found that workers slowly added about 13,139,034 cubic feet of soil to the complex, building it up over three centuries. In a similar vein, crews likely transported about 85,581,952 cubic feet of rock, dirt and adobe materials from nearby quarries to construct the city’s three major pyramids.

While a small number of Teotihuacán’s famous structures are preserved as an archaeological site, much of the surrounding eight-square-mile complex has since been covered by modern development. Researchers attempting to use LiDAR to study these areas were confronted with “extremely messy and hard to interpret” maps, notes Sugiyama in the statement.

In a ... city like Teotihuacán, the consequences of those actions are still fresh on the landscape.

What the maps did reveal was how closely modern buildings tended to adhere to ancient structures buried beneath the surface.

“[C]hanges made nearly two millennia ago still affect how we construct our buildings, align our roads, and terrace our crops,” Sugiyama tells Gizmodo.

Modern day rock fences in the farmland around Teotihuacán tend to be built along the same lines as older underground walls, reports David Nield for Science Alert. And 65 percent of urban areas in the footprint of the ancient city align with the direction of Teotihuacán, which was planned so that its major streets aligned with astronomical north.

“We don’t live in the past, but we live with the legacies of past actions,” says Sugiyama in the statement. “In a monumental city like Teotihuacán, the consequences of those actions are still fresh on the landscape.”

Archaeologists continue to unearth surprises at the site. Last month, for instance, a team discovered four exceptionally well-preserved flower bouquets in a tunnel beneath a pyramid dedicated to the plumed serpent deity Quetzalcóatl.

Each bouquet contained 40 to 60 flowers that bloomed sometime between 1 and 200 C.E. As Javier Salinas Cesáreo reported for Mexican newspaper La Jornada in August, the find marked the first discovery of preserved plant matter in Teotihuacán’s ruins.

Nora McGreevy | | READ MORE

Nora McGreevy is a former daily correspondent for Smithsonian. She is also a freelance journalist based in Chicago whose work has appeared in Wired, Washingtonian, the Boston Globe, South Bend Tribune, the New York Times and more.