Jambville and the Montcient Valley

Start from the car park at Jambville Castle (Scouts de France training centre).

(S/E) Facing the château, head east along Rue des Sports. Continue right onto Chemin du Cimetière.

(1) Cross Rue du Moustier and follow the path (Sentier du Marais du Val) downhill to Rue de la Côte Denise in Seraincourt. Cross Rue des Vallées.

(2) Turn left onto Rue de la Bernon (the Bernon river runs alongside this street) and follow the^GR®®2(red and white markings). Cross over to join the quarry path slightly to the left. Turn right and continue. A little further on, on your left, follow the^GR®®2uphill. Climb to the top to reach a T-junction.

(3) Take the path on the right.

(4) At the Y-junction, turn right and leave the^GR®®2. Head down towards Gaillonnet. Turn left onto the Chemin de la Hutte and cross the Montcient.

(5) Turn right onto the D913 (Rue de la Montcient) and immediately turn left towards the Seraincourt Golf Course. You are now on the Chemin de Dalibray; follow this until you reach a junction.

(6) Turn right until you reach the reservoir (on your right).

(7) Leave the road and take the path opposite, passing under the high-voltage power lines. Continue and head down towards Oinville-sur-Moncient via Rue de la Mathurine.

(8) Turn left at the corner of the church and walk past the school. At the top of the street, turn right. Continue, then turn left to reach the junction with Rue de la Chartre.

(9) Cross over and take the path directly opposite. Continue until you reach the junction with another path. Continue straight on (west) and follow a few bends until you reach the junction with another path.

(10) Turn right. At the next junction, continue straight ahead (west). You’ll come down to the junction with the D130 road.

(11) Cross the road (watch out for traffic). Ignore a path branching off to the right, then another to the left.

(12) Walk past the Malmaison farm, then take the path on your right (north). Continue until you reach the junction with Route de Guitancourt. Cross over to take the Chemin de la White Cross straight ahead. Walk past a shed, then turn right onto rural path number 37. This path leads you left onto Rue de la Carrière.

(13) Take the path opposite (do not turn right). At the Y-junction, keep left. At the next junction, continue roughly straight ahead (slightly to the right). At the next junction, turn right.

(14) At the junction with Route de Vetheuil (chapel), cross over to take Rue Saint-Laurent, then turn right onto Rue de l’Église. Cross the D130 to take Rue des Bonnes Joies. As you go uphill, turn right then left, cross Rue des Champs and head up to the woods via Chemin de la Croix Percée.

(15) At the next junction, turn right onto Chemin de Maigremont, then in front of Maigremont Farm turn right and continue straight down to the Cave aux Fées.

(16) Continue downhill. At the Y-junction, turn left to head back uphill.

(17) At the first junction, carry on straight ahead. At the second junction, carry on straight ahead again (north-north-west).

(18) Turn right and head down towards Montalet le Bois. Continue straight ahead, then cross the Route de Lainville and take Rue de l’Église.

(19) After the church, turn right. When the road bends to the right, continue along the path opposite. Cross the Bois de Jambville heading north-east, ignoring the side paths.

(20) At the junction, turn sharply right. Then turn left towards the Hazay farm. Go round the farm and head downhill to your right.

(21) At the crossroads, turn right. Now continue straight on until you reach Jambville Castle (S/E).

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Before doing this route by mountain bike, I did it on foot. It just took me longer.
Don’t forget to bring your own supplies (drinks, snacks, etc.) as you won’t come across any shops.