For centuries, a lost Mayan city lay buried beneath dense jungle in southeastern Mexico. The massive site, named Valeriana after a nearby lagoon, covers more than 16 square kilometers. With approximately 6,764 man-made structures, only the Calakmul site, located 100 km away, rivals its size.

Although it is a short walk from the town of Xpujil, the archaeological community was unaware that this ancient metropolis was hidden in the neighborhood.

Luke Auld-Thomas, a doctoral student at Tulane University, discovered it by chance. Searching the Internet, he found a laser survey by a Mexican environmental monitoring organization, “on something that looks like page 16 of a Google search.”

No other archaeologist has seen this. Auld-Thomas processed the data again, this time using parameters of his trade developed by the National Center for Airborne Laser Mapping.

The result was a detailed map of a sprawling lost city.

Founded before 150 AD

Even without fieldwork, the layout gives archaeologists a glimpse of what life would have been like in Valeriana. At its peak, between 750 and 850 AD, 30,000 to 50,000 people lived there. The downtown area included several pyramid temples, a ball field, enclosed plazas connected by a causeway, a reservoir, and amphitheater-style residential patios. Architectural details reveal that the city was founded before 150 AD and that the entire site was part of a continuous urban sprawl.

To the southwest of the city center is a more modest residential area. Here, ring-shaped structures revealed that the people who lived there produced lime plaster.

The epicenter of the site is at the edge of the area covered by the available data, making it extremely likely that there are other buildings just outside the scanned section.

This discovery reminds us that in precolonial times, complex civilizations lived in the tropics.

“No, we haven’t found everything, and yes, there is a lot more to discover,” Auld-Thomas said.

On every level, this discovery flies in the face of the old colonial idea that the Americas were a sparsely populated wilderness.

The future of discovery?

Valeriana also shows us the evolution of archaeological discovery methods. Light detection and ranging (LiDAR) technology penetrates dense vegetation. It can search for possible sites in huge and inaccessible areas. Until now, its prohibitive cost limited its use. However, as Luke Auld-Thomas has proven, archaeologists can reuse so-called “found” data sets from unrelated remote sensing work.

Who knows what ancient, undiscovered wonders are still out there, hidden in ancient civil engineering reports and ecological studies?