Lac des Brenets

Lac des Brenets, called Lac de Chaillexon on the French side, is a lake straddling the border between France and Switzerland, carved into the course of the river Doubs between Villers-le-Lac in the Haut-Doubs and the Swiss town of Les Brenets in the canton of Neuchâtel. It is one of the defining landscapes of the Jura border country: a narrow, winding stretch of water framed by forested limestone cliffs, shared and enjoyed equally by visitors from both countries.

How did this cross-border lake form?

The hollow occupied by the lake was shaped by glacial movement, and the lake itself came into being when a rockslide, roughly 12,000 years ago, dammed the Doubs valley naturally. Since then the river has pooled at this spot before continuing its course further downstream. The water is arranged into three basins, the lower two of which are known together as the Gorges du Doubs, where the channel narrows between steep, wooded cliffs rising to around 50 metres.

Why does the water level change so much?

The lake is fed solely by the Doubs, so its level tracks rainfall and snowmelt directly. Discharge can range from almost nothing to more than 300 cubic metres per second, and during prolonged dry spells the lake bed has been known to appear almost entirely, with the water nearly disappearing — this happened notably in 2018 and 2022. The phenomenon draws attention on both sides of the border whenever it occurs.

What lies at the far end of the lake?

At its downstream end, the Doubs plunges over the Saut du Doubs, a waterfall around 27 metres high. The site holds Grand Site National status and ranks among the most visited natural landmarks of the Franche-Comté region. A few hundred metres away, a bridge links the French and Swiss shores, allowing an informal crossing between the two countries on foot.

How can visitors explore the lake and the waterfall?

Electric sightseeing boats with an open upper deck depart from Villers-le-Lac, running narrated cruises along the meanders of the Doubs and across the lake itself. The round trip covers roughly 14 kilometres; a cruise without a stop takes about an hour, while a version that pauses at the viewpoints above the Saut du Doubs takes around two hours and fifteen minutes. Visitors who prefer to walk can reach the falls from the Vions car park via a marked trail of about 5 kilometres round trip with roughly 200 metres of elevation gain, leading to a series of viewpoints over the basins and the cascade. The long-distance GR5 trail also passes through the area, popular with hikers crossing the Jura.

What happens on the lake in winter?

When temperatures drop, the frozen surface of Lac des Brenets turns into a natural ice rink, locally described as one of the largest in Europe. Residents of Villers-le-Lac and Les Brenets keep a close eye on ice thickness to judge whether skating is safe; depending on the winter, the skating season can last anywhere from a handful of days to a few dozen.

Frequently asked questions

Are Lac des Brenets and Lac de Chaillexon the same lake? Yes. It is a single body of water — the Swiss name, Lac des Brenets, refers to the canton of Neuchâtel side, while the French name, Lac de Chaillexon, refers to the Villers-le-Lac side.

Which river forms the lake, and where does it go afterward? The lake sits on the river Doubs; downstream of it, the water drops over the Saut du Doubs waterfall and continues its course further into France.

Can you cross to the other country on foot here? Yes, a bridge over the lake connects the French and Swiss banks, and pedestrians can cross without a formal border check at this point.

Does the lake always stay full? No — because the Doubs' flow varies so much, the water level can drop sharply, and in extreme dry periods the lake has nearly dried up entirely.

Can a boat trip reach the waterfall itself? Yes, cruises departing from Villers-le-Lac head toward the Saut du Doubs, with an option to stop near the viewpoints overlooking the falls.