From Valmondois to Presles via the Forest of Isle-Adam and Pierre Plate

Starting point and access: Valmondois station.
- Transilien - Line H, on the sections between Paris-Nord and Persan-Beaumont via Valmondois, and between Pontoise and Persan-Beaumont.
Take the Place de la Gare exit (on the side of track 2, i.e. when arriving from Persan-Beaumont; if coming from the opposite direction, track 1, take the underground passage).

Yellow signage

(S) With your back to the station, head left, cross the main road (D4E), pass under an information sign with a map and follow the street that leads to the banks of the Oise (Rue du Port au Loup on the map). Continue straight ahead when the street becomes a one-way and ignore the private driveways on either side.

(1) Before a forest barrier behind which the river flows, turn right onto the tarmac road. Pass a metal barrier, walk alongside a water treatment plant and continue along a grassy path. At the crossroads, turn right (the purple line on the map is inaccurate here). After about 50 metres, turn left and walk alongside a football stadium. Pass through a heavy metal barrier (chicane), continue straight on Rue des Îles and ignore the side streets. At the stop sign, follow the D151 to the left and cross the Oise river on the road bridge. Ignore the arrow pointing down to the left (two^{PR® trails} intersect here) and continue to the crossroads.

(2) Cross the D922 in two stages (be careful, there is no pedestrian crossing) and follow it to the left towards L'Isle-Adam. Take the first right, a small road with a no entry sign. Continue straight ahead when it becomes a dead end. After No. 3, the tarmac gives way to a path that is closed to motorised vehicles.

No signposts

(3) At the crossroads, turn sharply left towards the Réserve du Marais de Stors. Ignore a green gate on the right and walk along a reed bed on your right. Continue along a wide path between two fences (wet passages). Ignore a path on the right behind a chicane and climb up with a wall on your left. Pass at the foot of a limestone bench and then under a stone bridge. At the corner of the wall, continue straight ahead.

Yellow markings

(4) At the T-junction, turn right.

Red and white + yellow markings

After less than a hundred metres (plot no. 87), follow the^GR®1straight ahead. At the next intersection, continue straight ahead. The path, bordered on the right by the remains of a wall, becomes narrower and more winding.

(5) Pass by some old quarries (do not cross the railings on the right-hand side, which is very steep). At the next intersection (plots nos. 83 and 82), continue along the path alongside the railings. After the railings end, turn left at the crossroads. At the T-junction, follow a wide forest track to the right. At the next junction, continue straight ahead uphill.

(6) At the fork, take the left path (ignore the yellow markings going to the right). After about 100 metres, turn left onto a good path between plots nos. 81 (on the left) and 79 (on the right). At the first junction, continue straight ahead. At the second junction, turn right and then immediately right again. At the next crossroads, continue straight ahead, veering slightly to the left, and climb up a sandy path with a sparse forest on your left. After a short steep, paved section, you will arrive at Carrefour Vicaire (signpost).

No signposts

(7) Continue straight ahead and follow Route du Sarcelet, which starts at the foot of the oak tree marked No. 75. At the next crossroads, take the second path on the left, Route Provost (no horse riding). At the next crossroads (plot No. 74), continue straight ahead. You will come to a crossroads with the impressive Chêne Provost oak tree opposite.

(8) Head east and take the second path on the right.

Yellow markings

At the next intersection, go straight ahead and take the footbridge over the N184. Continue straight ahead, go downhill and then uphill.

(9) At the crossroads (plots nos. 32, 35, 36 and 37), continue straight ahead along a recently cleared plot, where there are wet patches and well-marked ruts (situation in March 2018). At the next crossroads (plots nos. 36 and 37), turn right onto a discreet path (still some wet patches). Cross the D64 road and continue opposite, slightly to the right, on a path that crosses a dense undergrowth.

(10) Shortly before the clearly visible road, turn left at the junction near a pond. Cross a stream and climb slightly. When you reach the first houses, turn right onto the path.

(11) Cross the D64 at the entrance to Nerville-la-Forêt and climb the path opposite. After about 100 metres, at a crossroads, follow the same path, which immediately turns left and continues uphill. Walk along the walls or garden fences on your left. Cross a lane on the left-hand side (forest barrier) and join the^GR®1at the next intersection.

Red and white + yellow markings

(12) Follow the^GR® straight ahead along a fence on the left-hand side. Turn right at the foot of a large beech tree and then immediately left. Go down a steep slope and then back up again. At the corner of an isolated building on the left, turn sharply left, continue along the fence and walk alongside a field on your right (there is a beautiful large house opposite). Pass between two fences, come out onto a road and follow it to the left.

(13) At the crossroads, go straight ahead, go down Rue Marcel Harlay and ignore all the side roads. At the end of the tarmac road, continue along a grassy path (the "impraticable" sign applies to cars). Go down the embankment on the right-hand side, ignore a path coming from the left and pass a small pond on your left. At the N1 road, turn left onto a farm track, ignore a turn-off on the left and veer left to rejoin the road.

(14) Cross the D64E (take care, there is no pedestrian crossing) and follow it to the right towards Presles. Walk along the left-hand side of the road, behind the safety barrier. Follow the barrier to the end, go through a stop sign and you will immediately come to a crossroads.

Red and white markings

Continue with the^GR® on a grassy path that heads northeast between the small road to Beaumont-sur-Oise on the left and the D64E on the right.

Yellow markings (rare due to lack of support)

(15) At the crossroads (the "Slow down" sign does not seem to apply to pedestrians), turn right at an acute angle. After about 150m, you will find the Blanc Val covered walkway on your left. Retrace your steps.

(15) Back at the crossroads, continue straight ahead on a grassy path and pass a small green gate on your right.

No signposts

At the end of the path, turn right onto a small road (ignore the yellow arrow pointing to the left). Immediately cross a road on the right-hand side and turn left onto a farm track starting at the foot of a "No Entry" sign. At the junction with a very small road, go straight ahead towards a wood.

Yellow markings

(16) At the T-junction, turn left. Walk along the right-hand side, behind a fence, a wood and then a golf course. At the corner of the fence, follow the arrow on the right pointing towards Pierre Plate (ignore the other arrow pointing to the left). At the next corner of the fence, continue straight ahead. Climb the embankment of the path when it turns left and go straight towards the Pierre Plate covered walkway. The monument is fenced off, but there is an official opening that allows you to see it up close.

(17) Retrace your steps, this time following the fence on your left.

(16) At the intersection, go straight ahead. At the fork, two^PR® trails separate: take the one on the right. Very quickly, the tarmac replaces the path.

No markings

At the crossroads, continue straight ahead, pass at the foot of a calvary and immediately turn left along the cemetery.

Yellow markings

After a statue of the Virgin Mary, continue down the street, first on the pavement on the left and then, after the pedestrian crossing, on the pavement on the right.

(18) Before a bend, turn into a cobbled lane on the right and go down some steps. Cross a street and then the cobbled square between the church on the left and the war memorial on the right. Go down another flight of steps and turn left into the street at the side of the church. At the crossroads, turn right and go slightly downhill. Pass the Sports and Leisure Centre and, at the stop sign, continue straight ahead uphill. This will take you to Presles-Courcelles station (E).

To return home:
- Transilien - Line H, towards Persant-Beaumont (direct access) or Montsoult-Maffliers and Paris-Nord (take the underground passage).

Train timetables: consult the Transilien website.

For motorists:
The two stations are located on different sections of line H. There are two possible options:
- With at least two vehicles: leave one vehicle in the car park at each station.
- With only one vehicle: take the train one way or both ways, changing at Persan-Beaumont.
Both car parks are located on the opposite side of the railway line from the departure or arrival point: in both cases, simply cross the railway line at the level crossing.

Hiking boots are required. There are wet and potentially muddy sections between (3) and (4), between (9) and (11), and between (13) and (14).

A 1:25,000 map is required (at least the one accompanying this description).

Hike completed by the author on 29 March 2018.

- Reed bed between (3) and (4).
- Passage above old quarries after (5).
- Very pleasant walk in the Forest of Isle-Adam between (4) and (9).
- Some remarkable trees, including the Provost Oak (8).
- Blanc Val covered walkway near (15), modest in size and without covering slabs.
- Pierre Plate covered walkway (17), remarkable and in very good condition.