Modern roads and developments have more similarities to ancient urban centers than we realize. This is the case with Teotihuacan, a sprawling settlement that was once situated around 40 km (25 miles) northeastern of Mexico City.
Researchers used LIDAR ("light") and radar ("radar") scanning to discover that the contours and features of Teotihuacan, much of which is now obscured from view, are still visible in roads and structures built in the same place today, 1,500 years after it was constructed.
This study also revealed some amazing engineering done by Teotihuacan people: redirecting rivers to match points with astronomical significance and shifting large amounts of soil and rock to shape their city.
Nawa Sugiyama (anthropological archaeologist), from the University of California Riverside, says, "We don’t live in the present, but we live with past actions."
"In a massive city like Teotihuacan the consequences of these actions are still fresh in the landscape."
Teotihuacan, which covered approximately 21 km2 or 8 miles, was the largest city in the ancient world between 100 BCE to 550 CE. It included many plazas, pyramids, and commercial and residential buildings.
While some of the incredible structures at Teotihuacan remain, much of it has disappeared. LIDAR aerial mapping technology is here to help. It uses reflected laser lighting to measure underground structures and materials.
The researchers used a combination LIDAR, survey taken on foot and previously collected mapping data to compare ancient Teotihuacan with the Teotihuacan valley, which is now a UNESCO World Heritage Site.
The researchers found that 65 percent were home to property or features that are orthogonal within three degrees of 15 degrees east astronomical north, the exact alignment Teotihuacan was meticulously built to. Modern-day rock fences are built in the same way as ancient walls but now underground.
Today, the Teotihuacan valley. (Arian Zwegers/Flickr/CC-BY-2.0)
The ancient Teotihuacans invested heavily in rerouting rivers, and building canals. Researchers discovered that 16.9 km (10.5 mi) of the existing waterways had their origins in an Early Classical Teotihuacan area.
Researchers wrote in a published paper that "The Teotihuacan valley's unique environmental and cultural trajectories supports a multi-scalar description of humans as geomorphic agent."
According to the study, approximately 372,056 square metres (4,004,777 sq feet) of artificial ground were laid in the region over 300 years. There were 298 new features, 5 795 terraces made by humans, and more than 200 features that were once present but have been destroyed by mining.
The archaeologists continue to discover new secrets about Teotihuacan's history. We've seen previous researchers use the latest technology in order to reveal secret tunnels and ritual offerings at this ancient site.
This latest study shows that innovations and choices made more than a thousand years ago still have an impact on civilization. The team plans to extend their LIDAR mapping in order to cover a larger area in three dimensions and for a longer time.
"We can't fight modern urbanization," says Sugiyama. "The LIDAR map shows a snapshot of these old features that are disappearing at an alarming pace that would otherwise go unnoticed." It is one of many ways that we can preserve our heritage landscape.
The research was published in PLOS One.
