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Departure from the car park of the A.P. Vienot municipal swimming pool in Guyancourt.
(S/E) Exit the car park via the access road and turn left to immediately reach a roundabout with a sculpture. Go around it on the left and cross Rue des Graviers. Then follow this street to the left (north-west). Take thefirst right, Rue Allviger et Lanot, towards Bouviers. Note the information panel about the Bièvre landscape after the wall. At the bottom of the descent, cross the Bièvre.
(1) A few dozen metres further on, turn right into the woods, following theGR®11(red and white markings). Walk along the river on your right. At the end of the path, first turn left then right to follow the Sente de la Vallée (GR® markings). Then go down a staircase on the right (information panel and benches). At the bottom, turn left and take either a path or, further to the right, a boardwalk along the Bièvre. The two paths meet and pass in front of the Fontaine des Gobelins. Go through a gate and you will come to a crossroads.
(2) Go straight ahead and, after about 20 metres, turn left onto a path that climbs through the woods. After following the path for about 250 metres (uphill), continue straight ahead on the main path (do not take the path on the left, which is overgrown).
(3) At the T-junction, turn left and join the Route des Sangliers. Follow this path to the right with a fence on your left.
(4) At the fork, turn left and, at the next intersection, keep left (west) in the extension. Continue on Route des Sangliers, still with a fence on your left.
(5) Shortly before the N12, turn right and cross the Ru du Bois Robin. At the end of the bridge, turn right again. Follow the Route Forestière de la Fontaine Blanche and walk along the Ru du Bois Robert on your right.
(6) When you reach the Fontaine Blanche waterfall (often dry), turn right and cross the bridge over the stream. Ignore a steeply ascending path and follow a wide path to the south-west, which soon joins the Étang du Moulin à Renard (marked with red and whiteGR® signs ). Walk along the pond below on your left. Pass a reed bed and reach the crossroads you took on the way there.
(2) Turn left and cross the Bièvre upstream from the pond. Then follow the Chemin du Trou Chaud to the right. Walk along the right-hand side of a pasture with deer and horses. After the short climb, turn right and follow the fence on the right-hand side. Go through the gate and, at the end of the descent, cross the cattle grid.
(7) At the crossroads, turn left onto Chemin des Chevreuils. Climb the steps and go through the gate. Continue south, join Boulevard Jean Jaurès and follow it to the right. Cross Allée Gérard Philipe on the right-hand side. Then go around the crossroads on the right and follow the footpath that leads back to the swimming pool car park (S/E).
Visorando member
Moderate 
Difficult 
