Evrim Yazgin
Cosmos science journalist
A 3,000-year-old “mega fortress” in the Caucasus mountains has been mapped using drones, revealing the Bronze Age structure to be 40 times larger than previously thought.
The fortress, named Dmanisis Gora, is about 65km southwest of Tbilisi, capital of Georgia.
Dmanisis Gora was built between 1500–500 BCE. At the time, other massive fortresses were being built around the South Caucasus region. The construction of the mega forts marked a profound shift in the history of the area.
The region sits between Europe, Central Asia’s steppes and the Middle East. It has a rich history as a cultural crossroads and communities there were among the first to domesticate horses.
Excavations of Dmanisis Gora since 2018 revealed fortification walls scattered far beyond where archaeologists had believed the structure extended. It became clear that it wouldn’t be possible to determine the fortress’s true size from the ground.
“That was what sparked the idea of using a drone to assess the site from the air,” comments Dr Nathaniel Erb-Satullo from the UK’s Cranfield University and first author of the new paper on the study which appears in the Antiquity archaeological journal.
“The drone took nearly 11,000 pictures which were knitted together using advanced software to produce high-resolution digital elevation models and orthophotos – composite pictures that show every point as if you were looking straight down.”
Erb-Satullo’s team used a drone which has relative positional accuracy of less than 2cm.
The orthophotos were also compared with 50-year-old images taken by a Cold War spy satellite which were declassified in 2013. This helped researchers understand how the landscape has changed, including damage to the ancient settlement due to modern agriculture.
“These datasets enabled us to identify subtle topographic features and create accurate maps of all the fortification walls, graves, field systems, and other stone structures within the outer settlement,” Erb-Satullo says.
“The results of this survey showed that the site was more than 40 times larger than originally thought, including a large outer settlement defended by a 1km long fortification wall.”
Dmanisis Gora was 60–80ha (0.6–0.8km2) in size, making it one of the largest Bronze Age mega fortresses in the region.
“The use of drones has allowed us to understand the significance of the site and document it in a way that simply wouldn’t be possible on the ground,” Erb-Satullo says.
“Dmanisis Gora isn’t just a significant find for the Southern Caucasus region, but has a broader significance for the diversity in the structure of large scale settlements and their formation processes. We hypothesize that Dmanisis Gora expanded because of its interactions with mobile pastoral groups, and its large outer settlement may have expanded and contracted seasonally.
“With the site now extensively mapped, further study will start to provide insights into areas such as population density and intensity, livestock movements and agricultural practices, among others.”
