When archaeologists in Georgia were conducting test excavations at the 3,000-year-old fort, they were working in tall summer grass. When they return in the fall, however, they discover that the plants once hid something surprising.

Using drone technology, researchers in the UK, Georgia, and the US mapped the sprawl of Dmanisis Gora, a Bronze Age “mega-fortress” in the Caucasus mountains, and discovered that the complex was 40 times which is larger than previously suggested. Their research, detailed in a January 8 study published in the journal Ancientcan provide insight into the growth and urbanization patterns of ancient settlements around the world.

“The use of drones allows us to understand the importance of the site and document it in a way that is not possible on the ground,” said Nathaniel Erb-Satullo of the Cranfield Forensic Institute, which participated in the study, at a Cranfield University statement. “Dmanisis Gora is not only an important find for the Southern Caucasus region, but has a wider significance for the structural diversity of the major settlements and their formation processes.”

The Caucasus is a geographical region that includes parts of Russia, Georgia, Azerbaijan, and Armenia, and is an ancient crossroads of many different cultures, including local populations. Large-scale fortified settlements began to develop in the Southern Caucasus region between 1500 and 500 BCE, according to the study.

Erb-Satullo and his co-director, Dimitri Jachvliani from the Georgian National Museum and a participant in the study, began investigating Dmanisis Gora in 2018. After the initial test excavations, the team returned to find out that the autumn scene reveals more ramparts and stone structures far beyond the inner wall they saw before. The complex was apparently bigger than they thought—but they found it impossible to document just how big from the ground.

“That’s what sparked the idea of ​​using a drone to survey the site from the air,” Erb-Satullo said. The researchers used a drone to take nearly 11,000 photos of the site, which they combined to create digital elevation models and orthophotos: aerial photos corrected to account for elements such as angle from which the photo was taken.

“These datasets enabled us to identify subtle topographic features and create accurate maps of all the fortifications, tombs, field systems, and other stone structures within in the outer settlement,” added Erb-Satullo. “The results of this survey show that the site is more than 40 times larger than originally thought, including a large outer settlement defended by a 1 km long wall that fort.” Its base is about 0.62 kilometers wide.

Erb-Satullo and his colleagues compared orthophotos with Cold War-era spy satellite imagery declassified in 2013 to analyze how the site has evolved over the past five decades, highlighting the intrusion of modern agriculture.

Although modern expansion threatens the site, researchers hypothesize that thousands of years ago, Dmanisis Gora itself underwent impressive urban growth “due to its interactions with mobile pastoral groups,” explained Erb-Satullo. “The great outer settlement may be expanding and contracting with time,” he added.

Now, the team hopes to use the newly collected data to further examine elements such as population density and intensity, livestock movements, and agricultural practices.

Finally, drone mapping of Dmanisis Gora sheds light on the mega-fortress, as well as on the broader patterns of Late Bronze Age and Early Iron Age societies in general. This is also an example of declassified spy satellite imagery lending archaeologists a hand decades after the photos were taken.