Roman engineers had a simple philosophy about rivers: if one was in the way, you bridged it — preferably in a dead straight line, ideally before lunch. As our guide to Roman roads explains, when a route met water the legions simply drove timber piles into the riverbed and kept going. Now, beneath the modern city of Solothurn in Switzerland, divers have pulled the physical proof of exactly that out of the Aare: the waterlogged remains of a Roman bridge that has been quietly standing in the riverbed for roughly 1,700 years.
A discovery made before a railway upgrade
The find came out of underwater archaeology carried out ahead of renewal works on the SBB (Swiss Federal Railways) bridge. Divers working for the Cantonal Archaeology Office of Solothurn went down to inspect the riverbed near the Wengi Bridge, where earlier reports had vaguely mentioned wooden piles — the archaeological equivalent of “there might be something down there.” This time they got their answer. Timber samples from the piles were dated to the fourth century AD, confirming that a Roman bridge once crossed the Aare here around 1,700 years ago.
It’s a neat reminder that some of the best archaeology happens not on a glamorous dig but during routine infrastructure work — the Romans built a crossing here, and nearly two millennia later we’re still maintaining bridges over the same stubborn stretch of water.
Two wooden piles, the largest surviving elements of the Roman bridge, still rise about one meter from the Aare riverbed. Each measures roughly 20 centimeters in diameter. Credit: Kantonsarchäologie Solothurn / Carlos Pinto
What actually survives
Let’s manage expectations: this is not a dramatic stone arch looming out of the mist. The surviving remains are wooden piles embedded in the riverbed, sitting a short distance — about ten metres — from the southern bank, close to the modern Wengi Bridge. Archaeologists recorded a row of piles almost two metres long, neatly aligned with the direction of the current. They’re interpreted as part of a bridge pier (a “pile bent”) that would once have carried the timber superstructure and roadway. The largest surviving timber stands roughly one metre proud of the riverbed and measures about 20 centimetres across.
Modest? Sure. But these soggy stumps settle a question that had nagged at historians for decades. Everyone assumed there was a Roman crossing here — the road network and the river geography practically demanded it — but actual physical evidence from the riverbed had always been missing. Now it isn’t.
Salodurum: a town built on a crossing
To understand why Rome cared about this spot, you have to think like a Roman quartermaster. The settlement here was called Salodurum, and it grew up around movement. It was founded around AD 15–25 as a station on the road system linking the provincial hub of Aventicum (modern Avenches) with the legionary heartland on the Rhine — forts like Vindonissa and the colony of Augusta Raurica. That route was itself part of the great artery running from Italy over the Great St Bernard Pass, across the Swiss Plateau and the Jura, and onward to the Rhine frontier.
The Aare crossing at Solothurn slots perfectly into that system. Upstream the river meanders lazily; near Solothurn it pinches into a tighter channel — which is precisely where a sensible engineer builds a bridge. The name says it all: Salodurum is generally read as a Latinised Celtic name meaning something like a river narrows, a “water gate,” or “Salo’s fort” (the element -durum meaning fort or stronghold). The town is first attested in writing in AD 219, as vico salod[uro] on the so-called Eponastein. This was never a random riverside village; it sat exactly where a road, a crossing and a defensible landscape all met.
The bridge belongs to Solothurn’s fortress phase
That fourth-century date is the juicy part. It places the bridge firmly in the late Roman period, when Salodurum was transforming. The earlier open town of the first to third centuries — complete with temples and baths — was reshaped after around AD 300 into a fortified castrum. Late antiquity was a jumpier age: frontiers were under pressure, and settlements tied to roads and rivers increasingly grew walls.
At Solothurn, the bridge and the castrum almost certainly belonged to the same strategic thinking. A fortified town guarding a river crossing could protect traffic, control who came and went, and keep a vital route toward the Rhine secure. The new dating turns late Roman Salodurum from “small town on a river” into a deliberate node in a network of roads, soldiers and crossings.
A bonus: the martyrs of Salodurum
Roman Solothurn left more than soggy piles. The town is the legendary site of the martyrdom of Saints Ursus and Victor, two Christian soldiers linked in tradition to the Theban Legion, said to have been executed here around AD 286–300 under the emperor Maximian for refusing to sacrifice to the gods. Their cult was already going strong by the fifth century, when Eucherius of Lyon wrote up the story, and Ursus remains the patron saint of the city — his name carried by the great cathedral.
There’s a lovely archaeological footnote here too. When a sarcophagus said to contain the bones of Ursus was opened in 1519, it turned out to be a reused Roman coffin, its front carved with the inscription D(is) M(anibus) FL(aviae) Severianae — a dedication to a Roman girl, Flavia Severiana, who (judging by the coffin’s small size) had died in childhood. A pagan child’s burial, recycled centuries later for a Christian saint: Roman Solothurn in a single object.
Saved by luck (and waterlogging)
The piles very nearly didn’t make it to us. In 1969, river-correction works lowered and reshaped large stretches of the Aare’s bed near Solothurn, and ancient timbers could easily have been scoured away. The Roman piles seem to have survived simply because they stood in a sheltered pocket near the Wengi Bridge — archaeology preserved by sheer good fortune.
For now, the timbers will stay exactly where they are. Counter-intuitive as it sounds, the riverbed is the safest home for ancient wood: waterlogged conditions starve it of the oxygen that drives decay, while lifting the piles into the open air would be expensive and risky. Further dives are planned to hunt for more piles, which could reveal the bridge’s original alignment and how it was built.
Why this matters
Maps of Roman Switzerland have always drawn confident lines linking towns and forts, with rivers neatly bridged along the way. But a line on a map is a hypothesis, not a fact. What the Aare divers have done is convert one of those inked assumptions into hard, datable timber — the actual place where travellers, traders and soldiers once crossed the river in the age of Salodurum. Beneath the modern bridges of Solothurn, an older crossing still stands. The Romans, as usual, got there first.
Frequently asked questions
Where was the Roman bridge found?
In the River Aare at Solothurn, north-western Switzerland, near the modern Wengi Bridge. The remains sit about ten metres from the southern bank.
How old is the Roman bridge at Solothurn?
Wood samples from the surviving piles have been dated to the fourth century AD, making the bridge roughly 1,700 years old.
What was Solothurn called in Roman times?
Salodurum — a Latinised Celtic name usually understood to mean a river narrows or “water gate,” with the element -durum meaning fort or stronghold.
What remains of the bridge today?
Wooden piles embedded in the riverbed, interpreted as part of a bridge pier. The largest stands about one metre tall and 20 centimetres in diameter. They remain underwater for preservation.
Why is the discovery important?
A Roman crossing at Solothurn had long been assumed from the road network and river geography, but physical proof was missing. The dated piles confirm it and tie late Roman Salodurum into a wider system of roads, forts and river crossings.
Sources & further reading
- Ancientist, “1,700-Year-Old Roman Bridge Found Beneath Switzerland’s Aare River in Solothurn” (June 2026) — the discovery, dating and excavation details.
- Kantonsarchäologie Solothurn (so.ch) — the cantonal archaeology office that carried out the underwater investigation.
- Solothurn Tourismus / solothurn-city.ch, “History of Solothurn” — founding of Salodurum and its conversion to a castrum around AD 330.
- Wikipedia, Solothurn and Ursus of Solothurn — the Eponastein, the name Salodurum, and the saints.
- Ostia-antica.org, “Solothurn (Salodurum) — Tombs” — the reused Flavia Severiana sarcophagus.
- Britannica, Solothurn — the town’s growth around the Roman castrum.
