Pont Romain des Clefs

Pont Romain des Clefs is a stone bridge spanning the Fier river in the village of Les Clefs, deep in the Thônes valley in Haute-Savoie, a short distance south of Thônes and not far from Annecy. Despite its evocative name, the bridge has nothing to do with actual Roman engineering — it earned the nickname purely through its looks, above all the smooth, semicircular arch that carries it over the riverbed.

Why is it called the "Roman" bridge?

The bridge's single round arch has long reminded visitors of ancient Roman construction, even though it was built centuries after the Roman era. Local tradition long dated it to the 15th century, with construction placed around 1450 and a repair recorded in 1571. More recent research by historian Émilien Guelpa challenged that timeline, suggesting that the bridge at Les Clefs — like its neighbors at Thônes and La Vacherie — was actually built as late as 1734, by three contractors from Samoëns. Whichever date is correct, the "Roman" label stuck as a popular name rather than a historical fact, and it is how the bridge is known today.

What role did the bridge play historically?

Les Clefs was once the seat of a feudal lordship, held by a local noble family that shared authority over the Thônes valleys with the Counts of Geneva. Crossing the fast-flowing Fier mattered for trade and travel between villages, and the bridge was once subject to a toll collected from anyone passing over it. That practical role has since disappeared: no road or marked path leads to the bridge anymore, yet the structure has survived largely untouched, needing little to no major repair since it was built — a quiet testament to the skill of the builders who raised it.

What is there to see at the site?

The bridge sits tucked among trees and undergrowth, just above the point where the Champfroid stream joins the Fier. It's a peaceful, low-key spot, away from the busier trails of the Aravis massif, appreciated by walkers and landscape photographers who stumble upon it. The single stone arch rising over the water is the main draw — a rare, well-preserved example of the old bridge-building tradition of the Thônes valley. Its historical value earned it listing as a monument historique in 1947.

How do you get to the bridge?

Les Clefs lies in Haute-Savoie, only a short drive from Thônes and roughly half an hour from Annecy. Getting there by car means following local valley roads, and since the bridge no longer connects to any road or trail, reaching it involves a short walk from the nearest access point. It makes a natural stop for anyone combining a visit to the villages of the Thônes valley with a trip into the Aravis mountains.

Frequently Asked Questions

Is the Pont Romain des Clefs actually a Roman-era bridge? No. The name only reflects its appearance — the smooth, semicircular arch that resembles ancient Roman construction. Historians place its actual construction in the 15th century or, according to more recent research, as late as 1734.

Which river does the bridge cross? It spans the Fier river, in the Thônes valley, just upstream of where the Champfroid stream flows into it.

Can you still walk across the bridge today? The bridge no longer connects to any road or official trail, but it remains accessible on foot from a nearby road, and visitors can walk up to and across it.

Is the bridge a protected historical monument? Yes, the Pont Romain des Clefs was listed as a monument historique in 1947 in recognition of its architectural and historical value.