Park in the car park of the "La Sente des Carrières" primary school in Voisins-le-Bretonneux.
(S/E) Take Rue de la Mérantaise for 100 metres, heading south and following the forest on your left. On your right is the Chamfleury residence, the first American-style residence, built by Kaufman & Broad in 1970.
Take the first path on the left, at the gate marking the entrance to the Port Royal National Forest, towards the Croix du Bois. Continue straight ahead for 600 metres until you reach the Parc de la Croix du Bois.
(1) Enter the park through the entrance gate. Cross the park and exit through the main entrance to the north-east, behind the rose garden. Then turn right into the forest and continue for 200 metres. When you reach a crossroads, turn right and follow the path for 200 metres until you reach another crossroads. Turn left and follow the path for 100 metres. On your right, you will see a clearing with a large white wooden cross at the end.
(2) From this viewpoint, you can see the village of Magny-les-Hameaux and its bell tower. Turn around and take the main path on the right. You will soon reach the old sandstone quarries on your left, which have been in operation since the 18th century. Once you have passed the sandstone quarry, continue straight ahead, taking the path along the cliff for 200 metres.
Then continue along the path, which now zigzags downhill. When you reach a T-junction, turn right and continue for 30 metres until you reach a sign. Turn left towards Châteaufort and follow the Mérantaise to the Mérantais wash house.
(3) Cross the bridge and continue straight ahead south on Chemin des Patisiaux, which climbs up to the village of Magny-les-Hameaux. Enter the village and, after 100 m, you will see the Maison des Bonheurs on your right. Continue straight ahead until you reach the church on your right.
(4) Continue and turn left onto Rue Ernest Chausson. At the crossroads, take Rue Eugène Carrière on the right. Leave the village by continuing straight ahead along Allée des Pommiers, which will take you to the Domaine de Brouëssy after 500 metres.
(5) Take Rue Paul et Jeanne Weiss on your right, which descends for 300 metres. At the crossroads, keep left and follow Route de la Butte aux Chênes. Pass La Mérantaise and continue uphill for 300 metres. Just before the last left-hand bend, turn right to enter the forest at the wooden barrier. Turn immediately left and climb the path for 50 metres. Once at the top, head left and you will find yourself near the Hélène Boucher memorial.
(6) Continue along the path for 100 m until you reach the trail you took at the start of the hike. Turn left, exit the forest and continue to the right until you reach the car park (S/E).