An archaeological secret has been revealed in the Danube floodplains of Lower Austria: for the first time, researchers from the Austrian Archaeological Institute of the Austrian Academy of Sciences (OeAW) and the Carnuntum Archaeological Park of the Department of Art and Culture of the Province of Lower Austria have been able to prove the existence of a Roman bridgehead fort on Austrian soil. This discovery is proof for the importance of the Amber Road, a trade route which led from the Baltic via Carnuntum to the Roman Empire, and provides new details on Roman border defence along the Danube.

Until now, a comparable site on the Danube Limes was only known from the Iža-Leányvár fort in Slovakia. There was probably no fixed bridge in Carnuntum, but ferry services are documented until the 17th/18th century.

Roman border security and trade route control

»The still visible walls on the site known as the ›Ödes Schloss‹ were investigated as early as 1850,« explains Christian Gugl, archaeologist at the Austrian Academy of Sciences. »Based on the brick stamps found, the building structures were interpreted at the time as the remains of a fortified Roman bridgehead,« says Gugl.

But what exactly is a bridgehead fort? Usually built on the opposite side of a border river, they had the task of monitoring river crossings that were considered strategically important. From these bases, Roman troops were able to observe both the passage across the Danube and the surrounding countryside. Particularly along the Danube Limes, such installations were important for Roman border defence and the control of trade routes. The site is therefore also part of the Austrian Danube Limes, a UNESCO World Heritage Site since 2021.

Wall structures are remarkably well-preserved

The excavation in the ›Hainburger Au‹ brought to light remarkably well-preserved wall structures. Particularly impressive: parts of the fort walls are preserved up to 2.65 metres high. The scientific investigations show that the fort was built in two phases. The first phase dates back to around 170/180 AD, when Emperor Marcus Aurelius had the Roman border reinforced against the Germanic tribes during the Marcomannic Wars. In a second construction phase around the year 260 AD, the complex was refaced under Emperor Gallienus, but with the gradual loss of Carnuntum's importance, the number of troops also declined.

The archaeological finds include stamped bricks from legionary units XIV and XV, coins, pottery and some small bronze finds. »They prove the great strategic importance of Carnuntum within the Roman military system and provide new insights into the military security of the north-south connection,« emphasises Eduard Pollhammer, archaeologist and scientific director of Carnuntum.

Insights into the development of the Danube

In addition to the archaeological aspects, the excavation also provides valuable information on the dynamics of the Danube. As historical river courses before the 16th century are barely documented, sediment samples were taken in collaboration with BOKU University and the University of Vienna in order to analyse the geological development. Research into river morphology and the Anthropocene is thus being further intensified.

The excavations, which were carried out in the Donau-Auen National Park in 2024 with the support of the Austrian Federal Forests and in compliance with nature conservation regulations, have been completed. However, the scientific analysis of the finds is in full swing. The results promise exciting new insights into Austria's Roman past and the strategic role of the Danube Limes.

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