Archaeologists in Croatia have uncovered the remains of an ancient Roman watchtower dating back about 1,800 years. The structure guarded the Danube River frontier, known as the “limes,” a fortified border that once marked the edge of the Roman Empire.
Artifacts discovered at the site — including military gear, brooches, and ceramic vessels — suggest the watchtower was built in the late second century A.D. and remained in use during the third century, according to the research team.
“This is also the period of pressure on the Limes,” said Marko Dizdar, head of the excavation and a researcher at the Institute of Archaeology in Zagreb. It coincided with “the time of the Marcomannic War, when it was necessary to additionally protect the border on the Danube,” he said in an email.
Wars forced Rome to strengthen the frontier
The Marcomannic Wars, fought between A.D. 166 and 180, saw Roman forces under Emperor Marcus Aurelius battle several groups, including the Germanic Marcomanni north of the Danube and the nomadic Sarmatians from present-day southern Russia.
An almost Roman Czechoslovakia.
During Marcus Aurelius' war against the Marcomanni large parts of Czechia and Slovakia were occupied by the Roman army. Many temporary camps, a couple of permanent forts, and a massive central base with 11 square km of housing were built in the… pic.twitter.com/VyP0NBYfCe— LiorLefineder (@lefineder) April 2, 2025
The conflicts led Rome to establish military camps in eastern Croatia, at sites such as Sotin and Ilok. The newly excavated watchtower in the village of Mohovo is likely to have formed part of this defensive network.
“The watchtower was built in a strategic location, at one of the crossings over the Danube River,” Dizdar said. “From this position, there was excellent visual control of a large area, and it was also naturally protected on three sides by deep natural ravines.”
Researchers believe the tower was one link in a chain of signal stations spaced about two to three kilometers apart. Soldiers stationed there could send alerts to nearby towers and garrisons in Ilok and Sotin, roughly 12 kilometers away.
Excavation confirmed a defensive purpose
Archaeologists first identified the Mohovo site, along with about 10 others, during surveys conducted in 2003, 2013, and from 2020 to 2023. Their elevated positions along the Danube suggested a defensive role, although confirmation came later.
In 2020, geomagnetic surveys — a noninvasive technique that detects magnetic anomalies — suggested the presence of watchtowers and smaller fortifications. Trial excavations in 2024 confirmed these findings, leading to a larger dig in April 2025.
“This is the first systematically researched watchtower on the Limes in Croatia,” Dizdar said. “Until now, they were unknown, although it was assumed that they existed.”
Defenses evolved over centuries
The Mohovo watchtower measured about 130 by 100 feet (40 by 30 meters) and was protected by deep ditches and a wooden palisade, with a central wooden building. Evidence shows at least three construction phases, suggesting repairs and upgrades over time.
By the fourth century A.D., the tower was likely replaced by a smaller fort. Further excavations planned for next year aim to explore this transition.
Dizdar noted that Roman interactions shifted during this era. Trade with the Sarmatians gave way to stronger fortifications as Germanic tribes moved toward the Danube. “From the 4th century, larger forts were built and the number of soldiers increased,” he said.
The site holds layers of earlier settlements
The excavation is part of a broader initiative to protect Roman frontier sites and seek UNESCO World Heritage status for them. Researchers also uncovered remains from the Copper, Early Bronze, Iron, and Middle Bronze Ages, indicating the site was inhabited for thousands of years.
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