From Orgerus to Beynes along the Avre underground aqueduct

Starting point and access: Orgerus-Béhoust station.
- Transilien - Line N, on the section between Paris-Montparnasse and Dreux.
Take the Chemin du Moutier exit, on the side of platform 1 (Paris to Dreux direction). If arriving in the opposite direction, platform 2, exit on the side of the station building and take a small street on the left to join the route just after the bridge.

Red and white markings

(S) On leaving the station, on the Platform 1 side, head right and walk alongside the station car park (follow the^GR®22). After the bus stop, turn right, cross the bridge over the railway line and continue straight ahead. At the foot of the church, turn right onto Rue de la Mare Montigny and walk alongside the cemetery wall on your left.

(1) At the corner of the wall, turn left onto Rue de la Plaine and walk past the chancel of the church. Shortly after the junction with the underground Avre aqueduct (grass verge), when the street turns left, go straight on, pass a forest gate and continue along a grassy path with a hedge on your left. At the next junction, with a^PR® path (signpost), continue straight on along a stream and garden fences.

(2) Cross the D42 (take care) and continue straight ahead on the Chemin du Moutier. Immediately ignore a turn-off to the right, then cross a stream. At the next junction, just after a sewage treatment plant on the right, go straight on along a grassy path between the fields.

(3) Cross the D45 (take care) and follow the path opposite, slightly to the right. Walk north-north-east between the fields, ignoring a turn-off on the right and then one on the left. The path then descends between two hedges. Cross a stream via a wooden footbridge. Then climb slightly through the undergrowth. At a fork (not shown on the map), turn right (ignore the clearly visible red and white marker on the left on a forest gate; two^{GR® routes} split here).

(4) You’ll come out onto a small road; follow it to the right along the^GR®11. After a sewage treatment plant, the tarmac gives way to a track. Cross a small wood briefly, then walk alongside a wood on your right. Shortly afterwards, take a path on the left towards another wood.

(5) At the edge of the woodland, turn right (no arrow here but a marker further on on an oak tree) and walk along the left-hand side of the woodland. Cross the woodland briefly, continue along the edge and then through the fields towards the buildings of a riding centre. Ignore the private accesses on the left.

(6) At the end of the path, at the entrance to Flexanville, follow the D45 to the left (there’s a lovely gate on the right-hand side). At the fork (Place Roger Durain), turn right and walk past the church and then the war memorial. Then turn right into Rue du Pont, towards the cemetery. At the junction about fifty metres further on, turn left into the same street, which becomes a dead end. Continue straight on to the cemetery.

(7) Continue along a gently sloping path and follow the cemetery wall on your left. Cross a stream, either by fording it or via a small concrete bridge on the right-hand side. Head back up through the woodland opposite. At a three-way junction, turn left (no signpost here). Leave the woods and continue between the fields or along the edge. At a T-junction, turn right.

(8) At the fork immediately ahead, turn left. Immediately after, at a T-junction, turn left. Head north-east, ignoring the side paths, and alternate between walking through the fields and along the edge of the woods on your left.

(9) At the corner of a copse on the right-hand side, turn right. Follow a grassy path between the fields, ignoring a path branching off to the right, and reach the bench of the Avre underground aqueduct (a small masonry structure). Head due east and follow the embankment (very overgrown and unmaintained) on your right. Cross a stream, come out onto a small road and follow it to the left for about fifty metres (the purple route is not up to date).

(10) At the junction, follow the Route de Boulaincourt to the right. At a waterworks station, leave the road to the left and take the grassy path of the aqueduct. Pass through a metal gate, cross a small wood and then cross a small road.

(11) Then follow the aqueduct path eastwards through the Bois du Marmot. Depending on the season and conditions (height of the grass, mud, etc.), take either the path itself or a track running parallel to it. You will cross a^PR® path^. Pass a masonry structure and a metal barrier and, at the next junction, take the aqueduct embankment again, which here is a good dirt track. At the next junction (metal barrier; elevation 121), continue straight on along the aqueduct embankment. Leave the woods and continue along the heavily overgrown embankment. At the^first house, the aqueduct path becomes impassable (depending on the season): take a path on the right-hand side that runs parallel to it.

(12) At the end, turn left onto the Route de la Haye Frogeay, which winds through the village. At the foot of the church, turn left, leaving the war memorial on your right. At the Place du Rendez-Vous des Chasseurs, turn left to reach a crossroads (wash house).

No signposting

(13) Take the second road on the left, the Route des Châteaux, passing a small car park on your left and the wash house on your right (let the^GR® continue straight on towards Thoiry). Head north-north-west and ignore two turnings on the right.

Yellow markings

Before leaving the village, take a small lane on the right (Sentier des Plantes). The tarmac soon gives way to a path through chestnut woodland. You’ll come out onto a small road.

Red and white + yellow markings

(14) Follow the road to the left through the forest and rejoin the^GR®11. At the Stop sign, turn sharply right and pass through a forest gate. Follow a path heading south-east, ignoring a few side paths. Head downhill to reach the Chapelle Saint-Santin (spelled Saint-Sanctin on site). Leave the chapel on your left and continue along the edge of the woods on your left. Ignore a path on the right and head downhill.

Red and white markings

(15) At the three-way junction, take the left-hand path uphill and walk along the right-hand side of a small vineyard. At the next three-way junction (elevation 147; dense copse opposite), take the left-hand path, which is flat. Head due east along a grassy path to the D76. Follow this road to the right for about 150m ( ,take care, busy road). After a pond on the left, turn sharply left onto a gravel track. Continue along a grassy path. Cross the D11 (, take care) and continue along the path opposite towards the Forest of Beynes.

(16) After walking alongside the forest on your right for a few dozen metres, make a right-left zigzag to pass through a forest gate and set off along a path that is barely marked at the start (be careful). Walk directly under a high-voltage pylon. Pass at the foot of a second pylon on the right-hand side and turn right with the path (forest plot no. 10). Walk alongside a fenced-off plot on your right, then continue without a fence along a wider path. At a junction (plots nos. 9 and 11; small cross), continue straight ahead.

No signposting

(17) At the Carrefour d'Ex, take the second path on the left and walk past a gas installation on your right (let the^GR® continue straight ahead). Head downhill and, at the junction with a small tarmac road, continue straight ahead with a gas installation on your left.

Orange markings (rare)

(18) At the corner of the station (sign saying “3.5t”), turn right onto a bridle path. At the next two junctions, go straight on. At the third junction (gas installation some distance away on the left), continue straight on for about fifty metres.

No markings

(19) At the next junction (plot no. 4), continue straight on (east-northeast) and descend slightly. Ignore a path coming from the left and, at the next junction with a^GR®, take the path opposite which leads into the vegetation. Descend quite steeply along this narrow path. You’ll come out onto a small lane and continue downhill through a residential area. At the bottom, cross a main road and follow it to the left along its single pavement.

Red and white markings

At the junction at the entrance to Beynes, continue straight ahead. Ignore a street on the right then one on the left and, at the next junction, go straight on along Rue de la République.

(20) Take the^second street on the left towards the station and walk past the château on your right, then a car park. Cross the Mauldre and turn left with the road. At the stop sign, continue straight ahead and you will soon find Beynes station on your right (E).

To get back home:
- Transilien - Line N, towards Mantes-la-Jolie (direct access) or Plaisir-Grignon and Paris-Montparnasse (cross the tracks via the designated crossing, observing the traffic lights).

Train timetables: see the Transilien website.

For motorists:
Both stations are located on different sections of the N line. Two options:
- With at least two vehicles: leave one vehicle in the car park at Oregrus-Béhoust station (located on the side of the starting point) and one in the car park at Château de Beynes (this car park is more spacious than the station’s and saves you the short walk between the château and the station).
- With a single vehicle: make a return journey by train, changing at Plaisir-Grignon.

Hiking boots are required. Some sections are very overgrown (as of June 2018): between (3) and (4); between (9) and (10); before (12) where progress is difficult. Consequently, trousers are preferable to shorts.

Water point at Flexanville cemetery (7). Bar in Beynes, Rue de la République.

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

Hike undertaken by the author on 19 June 2018.

- Orgerus Church (12th and 15th–16th centuries), with its massive square Romanesque bell tower (1).
- Church of Flexanville (17th century) (6).
- Church of Autouillet (12th–13th and 16th centuries), between (12) and (13).
- Autouillet wash house (13).
- Château de Beynes (11th–15th centuries), partly in ruins and partly restored, shortly afterwards.