Fontaine Intermittente de Fontestorbes

Just off the road from Bélesta to Fougax-et-Barrineuf, there is a pretty grotto-like portal that the casual tourist could easily overlook. However, to do so would be to miss seeing a marvel caused by the area's unique hydrology. 

This site is known as Fontaine Intermittente De Fontestorbes, or the Intermittent Fountain of Fontesborbes. Water from deep within the surrounding limestone hills flows into the L'Hers-Vif river, but there's a twist. As the name suggests, it only flows some of the time.. 

It's striking to see how underground water fills a limestone basin before breaching its edge and cascading via a channel into the nearby river. The water then draws back, interrupting the flow. Then about 30 minutes later, the cycle starts all over again. 

The explanation for why this happens is complex and not fully understood. However, various studies have speculated that cavities deep within the escarpments above the fountain act as a natural siphon. The interaction of air pockets and underground reservoirs locks the water's journey to the surface into a perpetual ebb and flow cycle that tourists can enjoy all summer.

Indeed, this beguiling spectacle occurs only during the low water of the summer months as the subterranean waters strive to emerge into the light. During the time when the water is low, you can enter the dimly-lit cave via some precarious stepping stones to have a look at the internal rock formations as you wait for the show to start again. 

Recent upgrades to the attraction include a dedicated car park for visitors' convenience. There is also the curiously named Crapahut Parc Adventure center directly opposite, making what might be a brief stay to see a rare quirk of nature into a decent family day out.