Vallée Des Vaux

Vallée des Vaux is a scenic valley carved by the Ru des Vaux stream, spreading across the communes of Cernay-la-Ville, Auffargis and Senlisse in the Yvelines department, at the heart of the Regional Natural Park of the Haute Vallée de Chevreuse. This narrow gorge, with a marshy bottom in places and scattered with large sandstone blocks, forms one of the most distinctive landscapes southwest of Paris.

What can visitors see in the valley?

The best-known stretch, known as the Vaux de Cernay, runs for about five kilometers and includes ponds along with the ruins of the former Cistercian abbey of Cernay. Along the way, the Ru des Vaux stream tumbles over rocky ledges to form a series of small waterfalls locally called "bouillons de Cernay," a name referring to the frothing, bubbling water as it drops over the stone steps. The landscape also features former quarries and old watermills that once harnessed the stream's power, including the Petit Moulin des Vaux de Cernay, now partly restored and used as an interpretation center.

Why is this valley ecologically significant?

The valley is protected for the exceptional character of its biodiversity and scenery, and is listed as a ZNIEFF (a French designation for zones of ecological, faunal and floral interest) under reference number 110001488. The area combines meadows, woodland, watercourses and ponds, supporting a rich bird population — 148 bird species have been recorded here, including rare winter visitors such as the common snipe and the water rail, as well as very rare migratory species. The section within Cernay-la-Ville, known as the Petit Moulin des Vaux de Cernay, covers 3.2 hectares and includes meadow and woodland parcels, a watercourse, a pond, and the remains of the old mill buildings.

How to get there and what else to do nearby?

The valley lies close to the Rambouillet forest, within the Regional Natural Park of the Haute Vallée de Chevreuse, making it a popular destination for day hikes from the Paris region. Several waymarked trails cross the area, including a route connecting the Vaux de Cernay to the Rambouillet forest, as well as paths leading to the abbey ruins and the former quarries. Walks through the valley combine scenic highlights — steep slopes, rocky outcrops and waterfalls — with historical remnants such as the ruins of the medieval Cistercian abbey.

Frequently asked questions

What does "bouillons de Cernay" mean? It is the local name for the small waterfalls formed by the Ru des Vaux stream as it flows over sandstone blocks in the valley.

How many bird species live in the valley? Researchers have recorded 148 bird species in the area, making it a notable site for birdwatchers in the region.

Is the valley part of a larger protected area? Yes, the Vallée des Vaux lies within the Regional Natural Park of the Haute Vallée de Chevreuse and is classified as a ZNIEFF due to its biodiversity.

What historical remains can be found in the valley? The valley preserves the ruins of the former Cistercian abbey of Cernay as well as remnants of old watermills, including the partly restored Petit Moulin des Vaux de Cernay.