From Achères to Poissy through the Forest of Saint-Germain-en-Laye

Starting point and access: Achères-Grand Cormier station.
- RER - Line A, on the section between Paris and Poissy.
Take the only exit, at the front of the train when coming from Paris.

Yellow markings

(S) When leaving the station, turn left and walk along the N184 (four-lane road) on your right. At^{the first} crossroads, turn diagonally left onto a path that passes at the foot of an information sign and enters the forest. At the crossroads (stone cross), continue straight ahead, pass a forest barrier (blue cross on a white background) and continue south-east along a sandy path.

(1) At the next crossroads, take the^third path on the right, roughly opposite. Continue straight ahead and cross two successive crossroads.

No markings

At the crossroads (Étoile du Tronchet), take the^second path on the right and pass a shelter on the right-hand side. Continue straight ahead until you reach the Croix de Noailles road junction. Go around the junction on the right and, near the traffic lights, carefully take the cycle path to cross the N184. Immediately turn left onto a perpendicular cycle path to cross the D308 and follow the N184 towards Saint-Germain.

(2) At the foot of a lane narrowing sign, turn right, pass through a forest barrier and follow a path into the forest (plot no. 115). At the crossroads (Étoile du Grand Veneur), turn onto the^third path on the right (due west). The path narrows to become a trail (plot no. 163). Continue straight ahead and ignore all the paths on the right.

(3) At the next crossroads (Étoile du Dos d'Âne), you have two options:
- Take the^third path on the left (south-west). Go straight ahead, cross a small road and continue straight ahead to the point (5) (variant not tested by the author, which aims to avoid a path enclosed by vegetation).
- As shown on the map, continue straight ahead on a shaded path. Cross a small road and, on the other side, take the only path that appears (the path going west has disappeared). Continue straight ahead (south-west) on this path (not shown on the 1:25,000 map), which quickly becomes overgrown with vegetation. Pass a tree marked with the number 108 and join a perpendicular path.

(4) Follow this good path to the left and uphill. At the next crossroads (elevation 64), take the clear path on the right. Continue straight ahead until you reach the next crossroads (Étoile de la Charmeraie).

(5) Take the^third path on the right, roughly opposite. At the fork that appears shortly afterwards (plot no. 181), take the path on the right. Go straight ahead at the first crossroads and, at the next one, continue straight ahead between plots no. 174 and no. 172. At a poorly marked junction (not shown on IGN maps), turn left (horseshoe marker).

(6) At the next junction, at the boundary between plots 174 and 175, turn left. At the next junction, go straight ahead and, shortly afterwards, join a path coming from the right and continue straight ahead. At a crossroads, take the^{second path} on the right (south). In a left-hand bend, pass at the foot of the Croix Pucelle and you will immediately reach a T-junction.

(7) Turn left (blue cross on a white background). At the next crossroads (elevation 74), turn right and join the Étoile de la Mare à la Douzaine.

(8) Then turn onto the^second path on the right (south-west). At the end, go through a forest gate, cross a cycle path and then two parallel roads at several points using the protected crossings. Continue straight ahead on a small road lined with a fence on the right-hand side. Cross a bridge over a disused railway line and ignore a path on the left. When the road turns left, continue straight ahead on a path, still following the fence. At the junction at the corner of the fence, go straight ahead. Cross a tarmac driveway and continue on the path opposite.

(9) At the crossroads, turn right. Continue straight ahead (north-west) on a stabilised path, cross the tarmac driveway again and follow the fence on your right. Further on, cross a^GRP® (marked red and yellow) and continue straight ahead, ignoring the paths on either side. Follow the wall on your left and leave the forest through a gate in the wall.

(10) You will come out onto a street; follow it to the right. Cross Rue Pierre et Marie Curie on the left-hand side, continue straight ahead and take the next left, Rue Maurice Courtan. At the end, cross a busy street at the pedestrian crossing and follow it to the right.

(11) At the traffic lights, cross Avenue de la Maladrarie and follow it to the left. When the avenue turns left, turn right towards Lycée Le Corbusier and immediately turn right onto Avenue Théodore de Bèze. Stay on this road, which slopes downwards, and cross successively, on the right-hand side, Allées des Myosotis, Coquelicots, Marguerites, Bleuets, Pâquerettes and Jacinthes.

Red and yellow markings

At the "give way" sign, continue straight ahead on Avenue Christine de Pisan.

(12) At the corner of an old barn (information sign), turn right, enter the Abbey Enclosure and follow a cobbled street. Pass at the foot of a stone and brick building, then under a porch and continue between two walls. Pass under another porch, come out onto a wide street and follow it to the left.

No signposts

(13) After a slight left turn, cross the street at the pedestrian crossing, take Rue de l'Église and pass at the foot of the Collégiale Notre-Dame. Pass under a porch and continue straight ahead along Rue au Pain. Cross Avenue du Cep and continue straight ahead. Continue along Rue Jean-Claude Mary. Cross Avenue Victor Hugo and continue straight ahead. After exiting an underground car park, turn left, cross Avenue Maurice Berteaux and head for Poissy station (E).

To return home:
- RER - Line A, towards La Défense and Paris.
- Transilien - Line J, towards Mantes-la-Jolie or Paris-Saint-Lazare.

Train timetables: consult the Transilien website.

For motorists:
Both stations are on the same section of the same line. Park in the Poissy station car park (no car park found in Achères-Grand Cormier) and take the train there.

In dry weather, good trainers are sufficient for this route, which is mainly on well-maintained paths. In wet weather, hiking boots may be necessary.

There are no water sources along the route. Bars, restaurants and shops can be found in Poissy, between (13) and (E).

A detailed map is useful (at least the one accompanying this description).

Hike completed by the author on 12 November 2022.

- Pleasant forest paths from (S) to (10).
- Croix Pucelle (7), dated 1456 (year of Joan of Arc's rehabilitation), knocked down in 1793 and re-erected in 1848.
- Abbey enclosure, after (12).
- Notre-Dame Collegiate Church (11th-16th centuries) (13).