Start from the Bures-sur-Yvette train station (line B of the RER)
Yellow + Blue and White Markers (from the station exit)
(S/E) Take exit No. 1 "Impasse de la Station", which is the one located on the platform coming from Saint-Rémy-les-Chevreuse; if you come from the other direction (from Paris, for example), take the underpass. Upon exiting, carry straight on and then take an immediate right, then an immediate left through the Passage du Villevert. After a few metres, ignore the road veering to the left and enter the Parc de Grande Maison (through the gate or, if the gate is closed, through the little door to the left). Start opposite the downward slope of a wide gravel path.
(1) At a fork, ignore the right-hand path and continue straight on going down until you reach the water (with a large plane tree). Now turn left along the track lined by two rows of trees, with a channelled stream to your right. At the end of this track, (with the statue of Neptune), turn left and join the Rue de Royaume. At the end, turn right onto a tarmac road that soon veers to the left. Take the little tunnel that goes under the RER line and then veers right, opening out on an avenue (central car park).
Yellow Markers
Turn left, ignoring the markers (including a yellow one) that invites you to continue straight ahead on a small path (two different PRs at this point) and go up the Avenue Edouard Herriot until you reach the traffic lights.
(2) At the lights, cross the road and climb the stairs opposite. N.B. In this section, the purple line of the PR at the bottom of the IGN map is not accurate and there are more paths than are shown on the map. At the top of the stairs, in a forest, turn right on a path. Walk the length of the cemetery off to your left in the distance and and ignore the path to the right. At a fork (signposted "Boucle Trial"), take the right-hand path (south-southwest) which starts downwards. At a T-junction (signposted "Côte"), turn left and, at the fork which appears immediately, take the right-hand path. When you get to a crossroads (not shown on the map) take the second path on the left (southeast), which parts between forest plots 3 and 5 and climbs. After a left-hand bend, a final steep slope will lead you to the platform of an old railway line.
(3) Turn right and go in a southwest direction, ignoring several paths off to the side. Cross a small bridge and then a relatively short tunnel. Continue south-southwest until you arrive at the entrance to the Viaduc des Fauvettes (information board). Cross the viaduct and take in the height, particularly through two "wells" called "spéleos" (cavers) - practiced in the platform itself (be careful). After the viaduct, continue southwest through the forest. Just before a small bridge, leave the track and take a path to the left that goes up to the height of this bridge.
Red and Yellow + Yellow + Blue and White Markers
(4) Turn right to cross the bridge, walk down through the trees and come out on the edge of a field. Walk along the left-hand side (northwest), initially with a hedge to your left and then between two fields. Enter the forest and, contrary to the direction of two arrows, ignore two paths going off to the left and continue straight on until you reach a crossroads (small rocks, gate): this is where you need to turn left, on a path with fencing stretching along the right-hand side. At the end, pass a forest barrier and turn right into an alley that passes alongside a school. At the end of the alley, walk along the downward sloping path (a ramp). At the bottom, turn right and work your way between the garden fences with the Gometz-le-Châtel church in view up ahead. Walk back up until you reach a number of paths crossing.
''Red and Yellow + Yellow'
(5) At the crossroads, go up ahead of you onto the Chemin de Petit Huis (cement steps with a ramp: ignore the Blue and White markers that invite you to go left). At a fork, a few metres after the top of the climb, turn right onto Rue de l'Eglise and arrive at the church. Go down the steps close to the front of the church (find the Blue and White markers) and follow it left to the corner of the house called the Ortie Rouge (the “Red Deadnettle”). At the bottom, cross the road and, slightly to the left, take the Sente du Grimpé that goes under the porch of a brick-pink coloured house (be careful not to miss the passage).
(6) At the bottom of the descent, turn left and go up a wide avenue (D988) on the left-hand pavement. After the No. 119, cross a pedestrian-crossing and then continue to walk up the avenue. Before the Stop sign, take a sharp right into a dead-end. At the forest barrier, ignore the path going off to the left towards the glasshouses and join the path that turns right through the forest. Then walk in a north-northeast direction, first along the edge of a field (to your left) and a forest (to your right), then between two fields. At a fork, turn right and descend before you come out onto a road.
Red and Yellow + Yellow Markers (+ Blue and White intermittently)
(7) Turn left into the road and as you go up you'll immediately see a fork, go left onto the Avenue Claude Debussy. Follow this avenue straight ahead, going down and ignoring perpendicular roads until your reach a Stop sign. At the end, walk along a cement path sloping downward, cross a road and go back up a few metres. At the T junction, turn left. Just before a small car park (called "Bassin Armand"), leave the road, going past a forest barrier on the right and follow a wide track that goes up through the forest. When the Blue and White markers split off on a path to the left, continue straight up the wide track. At the top of the hill, turn right (east) onto another wide track (don't take the narrow path that turns sharply right).
Red and Yellow Markers
(8) At the crossroads (plot No. 100 on the right), turn left behind the large oak tree in the middle (ignore the Yellow markers as well as the Blue and White markers you'll see). Walk past a pond on your left, rejoin a gravel crossroads and continue north-northwest between plot numbers 93 and 90. At the next crossroads, continue straight on between plot numbers 78 and 85. At the following crossroads (where you'll see a laricio pine), take the second path on the right, downhill. Veer to the left when you reach a reservoir and continue downward. Pass a forest barrier, cross a track and keep going straight ahead (north) down the Impasse de la Terre Marnée. When you reach a junction with a road coming from the left, take a right along a small path, the Chemin du Couvent. At the next crossroads, turn left onto a road. At the end of this road, cross a perpendicular road and go down the stairs off to the right. Cross a wide road and reach the Gif-sur-Yvette train station.
(9) Take the underpass to cross the tracks and choose exit No. 1 . Then take a right along the Rue de la Croix Grignon, in the direction of the "Parc des Sports" (signposted). Ignore a small street to the left and then turn left at the fork. Cross the river Yvette and, immediately after, leave the road and walk down below to the left until you reach a crossroads of tarmac paths.
Red and White Markers
(10) Follow the GR655 to the right (ignore the GRP going off to the left) After a few metres, before you get to a car park, turn right through a tunnel under the road, with a stream on your left-hand side (a secondary branch of the Yvette). When leaving the tunnel, turn off left between two fences. At the crossroads (with a footbridge to your left), continue straight on. At the next crossroads, after a few metres, turn left and take the footbridge that crosses the stream. From here, stay east-southeast on the main track in the direction of Bures-sur-Yvette, ignoring paths going off to the left, and follow the markers as well as the street lamps that line the path. After about 1 km, veer right with the path to take a kind of embankment and cross the stream. Straight away, veer left and walk alongside a type of pond-spillway to your right. At a fork just after a very small building (the Maison de la Vallée de l'Yvette), ignore the wide track going right and take the left, narrower path towards a car park.
(11) When you exit the car park, turn left along the Rue de la Prairie (not signposted here). A the crossing shortly after, continue straight on down the Rue des Bleuets. Ignore the Red and White arrow inviting you to turn left along the Rue des Coquelicots and continue straight on until the end of the Rue des Bleuets (cross the Yvette just before the crossroads; you'll find the Red and White markers here). Turn right in the direction of the town centre (signposted centre-ville). At the fork (with an old building opposite), turn left, still towards the town centre, and use the right-hand pavement.
No markers
When you reach the market (located on the left-hand side), leave the road and enter the Parc de la Grande Maison to the right. At the first crossroads, take the second path to the right (not shown on the map) and quickly find the alley you took at the start of the walk.
Yellow + Blue and White Markers
(1) Follow the alley rising up to the left. Exit the park through the gate, continue opposite down the Passage de Villevert and turn immediately right to get back to the Bures-sur-Yvette train station (S/E).
