A recent aerial survey revealed thousands of ancient Maya structures previously hidden beneath the dense Guatemalan jungle, including houses, irrigation canals, fortifications, and even a pyramid. More importantly, though, the survey of 2,000 square kilometers of northeastern Guatemala provides a bird’s-eye view of the landscape of ancient Maya cities, farms, and highways. That big picture view of the Maya is letting archaeologists ask bigger questions about this still-enigmatic civilization.

A sense of mystery still surrounds the Maya, mostly because so much of their once powerful and sophisticated society now lies hidden beneath thick tropical foliage. In recent years, archaeologists have started using lasers to peer beneath the thick canopy of leaves and map the ancient Maya landscape from above. They’re using a technology called “light detection and ranging,” or LiDAR, which maps the height of features on the ground by measuring how long it takes infrared light beamed down from a plane to bounce off those structures and return to the instrument.

Using a plane lets surveyors cover a lot of ground in a short time, and one recent survey covered the largest area so far. The results hint that Maya civilization may have been more extensive and more densely populated than archaeologists realized. The survey, funded by the nonprofit Pacunam foundation, covered 2,000 square kilometers of northeastern Guatemala in 2016. Archaeologists have been poring over the data since early 2017, and they say they’ve discovered more than 60,000 new structures, from irrigation canals and highways to fortresses and pyramids.

It’s the scale of the survey, not the density of the finds, that has archaeologists so excited. The survey offers a look at the ancient Maya landscape in ways that have been impossible until recently.

Maya breadbasket

And that lets archaeologists ask big questions about ancient populations, economies, and agricultural sustainability. For instance, in the swampy valleys around the ancient city of Holmul, near the modern border with Belize, the LiDAR images showed thousands of acres of gridlike canal systems outlining raised blocks of land.

“These features are so extensive that it makes us start to wonder: is this the breadbasket of the Maya lowlands?” said archaeologist Tom Garrison of Ithaca College, whose team is working with the survey data. “Is this where they're growing so much... that maybe they're building an economy around it? Because where I work, close to Tikal, we have these features, but they're in smaller pockets.”

Mapping at this scale lets archaeologists consider how the ancient Maya supported such a large population and how cities like Tikal and Holmul were linked economically.

Today, the ancient farmland lies fallow in a region dominated by destructive slash-and-burn farming. But if the Maya once supported several million people by farming this swampy ground, archaeologists want to know how. The big questions, which archaeologists in the field will spend the next several years trying to answer, include exactly what the Maya grew in their irrigated fields and how they fertilized the otherwise inhospitable swampy soil around Holmul.

An ancient fortress

The ancient city of Tikal, west of Holmul, is now looking much larger than archaeologists realized. Defensive walls around Tikal were first discovered in the 1960s, but according to the new survey data, those fortifications are more extensive than previously thought.

“The LiDAR really revealed this big earthwork in a much more comprehensive way than we'd seen before, including areas where previous teams had maybe thought that there was no wall,” said Garrison. In some places, water drainage has worn down the earthwork walls until what remains is such a subtle rise you couldn’t see it even if you were standing right beside it—but it’s clearly visible from the air with LiDAR.

“There has been substantial evidence of warfare in the Maya area. But the fortifications that they found are amazing. These finds will be significant contributions to the study of Maya warfare,” said archaeologist Takeshi Inomata of the University of Arizona, commenting on the survey results. “The specific interpretations will depend on the dates of those sites and their social contexts, which need to be studied through excavations.”

Garrison and his team are planning to do just that. They’ve already spent a season in the field, and he says they’re planning to return for more thorough excavations of the Tikal earthworks.

Getting their hands dirty

Even with good remote data, archaeologists have to do what’s called ground-truthing: making sure that what they think they see in the LiDAR images matches what’s actually on the ground. And they also have to get their hands dirty in order to study the kinds of details that don’t show up from the air: things like how old a building is and when it was used.

Looking at the LiDAR image is like looking at 2,500 years of shifting, moving human occupation all compressed into one snapshot. The images show 30 or 40 structures per square kilometer, but those structures weren’t all built or used at the same time. One of the big tasks facing Maya archaeologists now is figuring out which of the buildings, fortifications, and canals were used when. That will have important implications for figuring out how many people lived in the Maya lowlands at any given time.

Fourteen of the archaeologists who received data from the project say they’re planning to submit a paper to a journal in the next few weeks describing some of the fieldwork they’ve done in response to the images. But ahead of the paper, they’re sharing some of their findings with the public in an upcoming National Geographic special on Tuesday, Feb. 6 at 9 p.m. EST/8 p.m. CST., which includes footage from both the 2016 survey and the 2017 field season.

LiDAR is gaining ground

This is one of the largest-scale archaeological LiDAR surveys so far, but it’s not the first. In 2009 and 2010, archaeologists Arlen and Diane Chase pioneered the technique in Belize. And so far Richard D. Hansen, director of the Mirador Basin Project in northeastern Guatemala, and his colleagues have mapped 750 square kilometers of the largest, earliest Maya cities in the Mirador-Calakmul basin, which archaeologists think is the original home of the Snake Kingdom. They plan to continue LiDAR surveys there in March 2018.

“We spent more than $1 million and 15 years in mapping [52 square km] of the Mirador Basin with sophisticated Total-Station laser mapping systems, and our LiDAR data quickly surpassed that research in exponential fashion with 38 hours of flights,” said Hansen.

As more Maya archaeologists start using LiDAR, Pacunam hopes to encourage researchers in Guatemala, Mexico, Belize, and Honduras to share their survey data. Hansen, who helped found Pacunam, says his team plans to contribute. Meanwhile, the Pacunam survey flights have so far covered only a 10th of the 20,000 acres the foundation wants to map over the next few years. But as technology sheds new light on the Maya landscape, it illuminates as many questions as answers about the people who once lived here.

“What’s exciting about this technology is it tells us more about [Maya culture] than we’ve ever known, but it also still leaves some of that mystery for us: these things that we can’t totally explain that need to be researched,” said Garrison.