Regional Natural Park of the Haute Vallée de Chevreuse
The Vallée de Chevreuse is in fact the valley of the Yvette River, a small tributary of the Orge.
It remains a great green lung just 30km from Paris, although dreamers like Alphonse Allais wished for new towns in its countryside, as 'the air is so pure here'. Now the valley is reputed for its hiking and draws tourists thanks to its fine heritage, such as the Château de Breteuil and the Abbey of Port-Royal. Since the 1950s, the valley has also become home to a major European science park.