Archaeologists using an old map of Mexico’s Yucatán Peninsula have discovered a lost, hitherto hidden Mayan city with thousands of buildings densely packed into a small area.

The archaeological team used a lidar survey (short for “light detection and measurement”, a foundation of modern archaeological techniques) to identify nearly 7,000 previously undiscovered structures, including pyramids like those found elsewhere in Central America. The team’s research, detailing these findings, was published today in Antiquity.

Lidar surveys are very useful in Mesoamerican archaeology, where jungle areas can quickly engulf entire cities. Three years ago, a separate team mapped 30,000 square miles (78,000 square kilometers) of Mexico, comprising nearly 500 historic sites, and found that similar design patterns were used for cities in the region.

Lidar can even shake up archaeologists’ understanding of thoroughly surveyed sites; in 2021, a lidar survey of Tikalin Guatemala, revealed a previously unknown neighborhood complex on the sprawling site.

However, lidar is expensive. That’s where an old map comes into play—a 2013 lidar survey of the region, specifically, commissioned by a group that monitors carbon pools in Mexico’s forests. The recent archaeological team had access to that data, saving them from an expensive new scan of the region. The team interrogated the 2013 map for evidence of previously undocumented Mayan settlements and found more than they bargained for: 6,674 previously unknown structures in Campeche.

“Our analysis not only revealed a picture of a region that was dense with settlement, but also revealed a lot of variability,” Luke Auld-Thomas, an archaeologist at Northern Arizona University and lead author of the paper, said in a study. Antiquity press release. “We didn’t just find rural areas and smaller settlements. We also found a large city with pyramids right off the only highway in the area, next to a city where people have been actively farming among the ruins for years.”

The data only covered a region of about 50 square miles (129 square kilometers), but the area was full of ancient architecture. The researchers were also able to identify specific structures in the lidar that made up the Maya city, including a ball field and a dam. An architectural arrangement at one of the sites indicated a foundation date prior to AD 150, according to a previous study. This is slightly earlier than the Classic Maya period, which spanned from AD 250. to 900 AD.

“The government never knew about it; the scientific community never knew about it,” Auld-Thomas said. “That really puts an exclamation mark behind the statement that, no, we haven’t found everything, and yes, there’s more to discover.”

In the paper, the team noted that the recent data provided support for the previously stated concern that “archaeologically motivated lidar studies have inflated regional settlement density estimates.”

“In contrast, pseudorandom surveys—those that combine opportunistic and random sampling—like this one have established that anyone expecting a sparsely settled Maya hinterland large enough to offset the high settlement densities documented by archaeological lidar surveys is running out of places. to look,” the team added. To put it simply: the data set the team recently used was not collected with an archaeological objective, but rather supported previous ideas about Maya urban sites and their density.

While lidar surveys are great for discovering sites and making guesses about the layout of cities, the aerial approach to archeology can’t replace old-fashioned fieldwork. right Antiquity launch, future research will focus on fieldwork at the locations. Considering there are nearly 7,000 structures in the area, the research could take some time.