A collection of silver coins sold on the black market has led European archaeologists to the discovery of a monumental prehistoric fortress.
The 3000-year-old site, hidden away in the Papuk Mountains of eastern Croatia, presents previously unknown evidence of complex fortifications that once existed in the region.
Located 611 meters above sea level, the Gradina site was discovered after reports involving the illegal excavation of “silver coins from Voćin” began surfacing amid Europe’s illicit antiquities markets. Efforts to track down information about the looted coin hoard ultimately helped lead archaeologists to the long-overlooked Croatian site.
Excavations Underway
Currently, excavations at the site are being led by Hrvoje Potrebica, a professor of prehistoric archaeology at the University of Zagreb. Working with colleagues, including researchers Franka Ovčarić and Luka Drahotusky-Bruket, systematic surveys and initial excavations at the site revealed the presence of stone ramparts and other features.
The site is now believed to potentially be one of the best-preserved prehistoric settlements ever uncovered in the region.
“These are some of the most visible ramparts, very well preserved, of a prehistoric settlement in this part of Croatia,” Potrebica said in a statement.
“Usually they were built of earth and wood, so they fell into disrepair,” Potrebica added, “but here it is different.”
An Ancient Site Emerges
Initial assumptions suggested the site dated to the La Tène culture of the late Iron Age, around the 1st century BCE, consistent with the Celtic silver coins first linked to the area.
That all began to change for Potrebica and his colleagues as their investigations continued, revealing discoveries that hinted at a much deeper origin for the ancient site. These included ceramic fragments the team uncovered, dating to the Late Bronze Age, roughly 1200 to 1000 BCE.
“These findings are very rare,” Potrebica said, adding that the ancient fortress structure encloses an area estimated to comprise four hectares.
“At one point we decided to cut through the rampart, and we established a monumental construction consisting of three layers, earth, stone, and rammed earth, up to 2 meters high, in some places 7 to 8 meters on the outside,” Potrebica said.
A Remarkably Well-Preserved Site
In some sections, the archaeologists also uncovered a dry-stone defensive wall more than 1.5 meters thick, an exceptional level of preservation for prehistoric fortifications in this part of Europe.
Most prehistoric settlements in the region relied on perishable materials, including earth and timber defenses, and thus have largely deteriorated over time. The stone-built ramparts at Gradina, by contrast, remain clearly visible on the landscape, marking the site as a significant outlier.
This suggests a level of organization exhibited by its ancient builders, the likes of which had never been documented previously in the region during this period. Additionally, evidence of domestic structures and other signs of daily life point to its apparent use as a long-term habitation site.
“Here, at this place, we did not expect anything like this,” Potrebica said, adding that the team’s discoveries were unlike anything he had encountered in his profession in the last quarter century.
Fundamentally, the site’s rediscovery underscores both the scientific potential—and the risks—associated with illicit antiquities trafficking. Although illegal looting by metal detectorists at the site helped lead to its discovery, such activities also destroyed the original archaeological context of the artifacts removed.
Nevertheless, in this case, the removal and eventual black-market sale of coins from the ancient site led archaeologists to a novel discovery—one that is expanding our knowledge of the region’s inhabitants’ activities long before Roman or medieval times.
For Potrebica, the discoveries his team has made during their excavations are truly one of a kind.
“I have never seen anything like this,” Potrebica said.
Additional details about the team’s discovery, along with photos of the ancient site, can be found here courtesy of vpz.hr and Kristijan Toplak.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.