Swiss archaeologists have discovered the remains of an ancient Roman bridge that crossed the River Zihl in Aegerten in the Canton of Bern. The discovery, made during construction work, uncovered over 300 preserved oak piles in the waterlogged soil of the former riverbed.

Several oak pile tips, each several meters long, have been preserved and were pulled from the sediment using an excavator. Credit: Archaeological Service of the Canton of Bern, Joel Furrer

The bridge was part of the Roman Jura Transversal, an essential transport corridor between waterways and land routes on the Swiss Plateau and through the Jura mountains to Augusta Raurica, one of the oldest Roman colonies on the Rhine. Strategically, it was located just outside Petinesca (now Studen), a Roman station settlement that supported and protected travelers moving between Aventicum, Vindonissa, and the Rhine frontier defenses.

Dendrochronological dating suggests that the earliest bridge construction dates to around 40 BCE, soon after Rome had conquered the Helvetii Celtic confederation, which had controlled most of the region. The bridge continued in use for centuries with continuous repairs and reconstruction. The final construction phase can be dated to CE 369 under Emperor Valentinian’s reign, when Rome consolidated its northern frontier in response to growing Germanic incursions.

The wooden piles were not the first evidence of a Roman presence in the area. Archaeologists discovered Roman military structures on both banks of the Zihl River forty years ago. That earlier discovery helped guide today’s excavation works when new construction began. Taking advantage of breaks in the construction schedule, specialists were able to document the remains, extract samples for laboratory tests, and recover ᴀssociated artifacts without causing delays.

Excavation showing closely spaced oak piles from the bridge bays. A sample was taken from each pile for age determination. Credit: Archaeological Service of the Canton of Bern, Joel Furrer

Excavations in the riverbed silt have yielded an extensive range of artifacts related to everyday life and commuting over the bridge. They include hobnails from soldiers’ footwear, horseshoes, harness fittings, axes, coins, keys, and even a fishing trident. Most of these artifacts appear to have been deliberately discarded from the bridge, probably as offerings, while others may have been lost by travelers.

Among the most dramatic finds is a large carpenter’s plane made of wood with an iron blade. The tool was exceptionally well preserved owing to the oxygen-poor, damp soil. Along with the other artifacts, it gives a glimpse of the practical realities of Roman transportation, trade, and craftsmanship.

The fully preserved carpenter’s plane, carved from a single piece of wood with an inserted iron blade, measures 41 cm long, 7 cm wide, and 5 cm high. Credit: Archaeological Service of the Canton of Bern, Joel Furrer

Experts point out that the finds are now being conserved and studied, and they could provide important insights into Roman infrastructure engineering and the everyday existence of individuals who lived and traveled through the region. The bridge’s long history—more than 400 years of continuous use—emphasizes its critical function in connecting settlements and maintaining Rome’s presence north of the Alps.

More information: Archaeological Service of the Canton of Bern