Country:
District:
Starting point and access: Orsay-Ville station.
- RER - Line B, on the section between Paris and Saint-Rémy-lès-Chevreuse.
Take exit 1 Boulevard Dubreuil, on the side of track 1, in the direction of Paris to Saint-Rémy-lès-Chevreuse (if arriving in the opposite direction, track 2, take the underground passage).
N.B. The OSM map background was chosen because the IGN background contains several inaccuracies in the Bois de la Grille Noire crossing.
No signposts
(S/E) With your back to the station, leave the car park on your right, cross Boulevard Dubreuil and follow it to the left. Just before a restaurant, turn right, go under a porch and go up Passage du Chemin de Fer (a series of steps followed by a sloping alley). At the end, at a roundabout, take thefirst left downhill, Rue Jean-Louis Archangé.
(1) Turn right at thefirst street, Ruelle des Cordiers. Immediately turn left into Allée Louis-Clément Faller, go down a flight of steps and pass under a building. Follow the alley straight ahead, ignoring the turnings on the left. At the end, turn left and, at the corner of the post office, turn right into Rue de Paris.
(2) When the street curves to the right, leave it by continuing straight ahead and passing under the Porte de la Grande Bouvêche (do not follow the Allée de la Bouvêche diagonally to the left). Go through a gate and enter the garden of the cultural centre. Go around the building on the right (well) and, at the corner, climb the stairs on the right that lead to a car park.
Turn left and cross the car park. At the end, turn right (signposted "Sortie") and go up a small street. At the end, you will come to Rue de Paris. Follow it to the left. Take a side street on the right to pass under the N118 bridge.
Yellow markings
Just after the bridge, turn right onto a tarmac path bordered by a wall and then a wire fence on the left. Turn left with the path, walk alongside the buildings and then wind your way through the undergrowth.
(3) At a fork, turn right and climb steeply. At the top, turn right and take the narrow tunnel under the D188. At the junction immediately after the tunnel, turn right and follow the path around a wide bend to the left. Ignore a path on the left, make a wide turn to the right and climb slightly. At the top, turn left and climb more gently, overlooking the N118 on your right.
Yellow + red and green markings
(4) At the crossroads (bench), turn sharply left and uphill, following thePR®10(twoPR® trails intersect here). Ignore a path on the right and, at the next fork, climb steeply to the right. Immediately turn right (east) and continue on a wide, fairly flat path, ignoring the paths branching off to the right. You will come to a large crossroads at the edge of forest plots nos. 7, 11 and 12.
(5) Take thefirst pathon the left (on the side of plot no. 7) and follow thePR®2(leave thePR®10, also marked in yellow, and continue straight ahead). Descend comfortably on a wide gravel path, ignoring the vague turnings on either side.
When you reach the D188, turn left (do not go as far as the forest barrier). Immediately turn right to take another narrow tunnel. At the exit, continue straight ahead for about 100 metres.
(6) At the three-way junction, turn right towards a house. After about 50 metres, turn left and then immediately left again. Ignore a path on the left and continue straight ahead at the crossroads. Wind your way through the undergrowth and finally turn right (north-east) to join Rue de Paris at a crossroads. Follow the street to the right until you reach the traffic lights.
Cross Rue de Paris and take Rue Mademoiselle towards the rugby stadium. Continue straight ahead down a steep slope to the bridge over the River Yvette.
Yellow + red and white markings
(7) Just before the bridge, turn left onto a tarmac path and follow the river on your right. Pass the entrance to the rugby stadium and continue along the river (note Lac de Lozère on the other bank). After a football stadium, at an intersection, continue straight ahead, where the tarmac gives way to a stabilised path. Pass through a forest barrier and you will come to a roundabout.
Red and white markings
(8) Go straight ahead (leaving thePR® trail on your left) and cross thefirst slip road to the N118 at the pedestrian crossing. Pass under this four-lane road and cross asecond slip road. Continue along the river and, just before a 30km/h zone, reach the riverbank. Go under a small road bridge. Further on, join the street, follow it to the right and go under the railway viaduct.
You will arrive at Lac du Mail. Go around the lake on the left (ignore a red and green arrow indicating a right turn). Pass a playground on your left and, at the end of the lake, take a footbridge over the Yvette on the left. At the exit, turn immediately left. Follow a path between the river on your left and the swimming pool on your right. When you reach a road, turn left to cross the Yvette one last time.
No markings
Follow Rue Élisa Desjobert diagonally to the left towards Bures-sur-Yvette. Cross Rue Launay and continue up the street towards the sign for the RER. At a left-hand bend, leave the street and turn right towards Orsay-Ville station (S/E).
To return home:
- RER - Line B, towards Paris (immediate access to platform 2) or Saint-Rémy-lès-Chevreuses (take the underground passage to platform 1).
Visorando member
Moderate 
Association / Club / Walk leader
Very difficult 
Difficult 
