Grotte Sarrazine

Grotte Sarrazine is a karst cave in the commune of Nans-sous-Sainte-Anne, in the Doubs department of eastern France, in the Bourgogne-Franche-Comté region. Its entrance sits at the foot of an enormous rock archway cut into a Middle Jurassic limestone cliff, and it's really that archway, more than the cave itself, that draws hikers exploring the springs of the Lison river.

What makes this spot stand out?

The dominant feature is a huge arched porch, roughly 100 metres high and 30 metres wide, shaped like a vertical half-cylinder capped by a dome. The cave mouth opens at its base, and during heavy flooding water surges directly out of it. Grotte Sarrazine belongs to what's known locally as the "site du Lison," a trio of natural landmarks that also includes the Lison spring and the karst sinkhole called Creux Billard. The whole area has been protected as a landscape site since 1946.

How did the cave form?

Grotte Sarrazine works as a natural overflow outlet for the Lison spring. Under normal conditions, the river simply emerges from the main spring further down the valley, but after heavy rain the underground karst network can't absorb all the incoming water, and the surplus forces its way out here instead. This flood surge has a local name, the Bief Sarrazin, and it can reach flow rates of around 16 cubic metres per second — an impressive sight for anyone who happens to visit after a storm.

Beyond the entrance lies a network of underground galleries that has been mapped for more than 4 kilometres. The passage begins with a gallery roughly 2 metres high and 10 metres wide, opening onto a small underground lake. Outside of flood periods, most of this network stays dry.

Can visitors go inside the cave?

Reaching the entrance and admiring the rock archway from outside is open to any walker following the marked path. Venturing into the cave system itself is a different matter: given its complex layout and the risk of sudden flooding during storms, exploring the interior is left to experienced cavers, ideally in organised groups with proper equipment.

How to get there

The usual starting point is the Lison spring, from which an easy, flat path of about 500 metres leads to the cave. Many visitors combine the stop with a longer walk through the area — a loop taking in the Lison spring and looping back to the village of Nans-sous-Sainte-Anne runs about 5 kilometres, takes roughly an hour and a half, and gains only around 120 metres of elevation, making it suitable for families. Nearby, it's also worth seeing the Pont du Diable and the waterfall on the Lison river.

FAQ

Where is Grotte Sarrazine located? In the commune of Nans-sous-Sainte-Anne, in the Doubs department, close to the springs of the Lison river.

Can you visit the cave without a guide? The exterior — the entrance and the rock archway — yes, via the path from the Lison spring. Going inside requires caving experience and isn't meant for casual visitors.

Where does the water inside the cave come from? It's a natural overflow of the Lison spring, triggered during heavy rainfall when the underground karst system can't handle the extra volume.

How long does it take to reach the cave? From the Lison spring it's only about 500 metres on an easy path; the full loop around the area takes roughly 1.5 hours.

Is the site protected? Yes. Together with the Lison spring and Creux Billard, it forms a landscape site that has been under protection since 1946.