La Roche-Guyon: the castle, the forest, the flint cliffs
Walker 
15.38 km
+345 m
-348 m
5h 25
Moderate
Departure from Amenucourt (Val-d'Oise)
A very varied hike that combines:
- Regional Forest of the Roche-Guyon,
- A beautiful, quiet valley,
- The town of La Roche and its castle,
- and finally, a scenic route overlooking the Seine.
The Dolmen of Bois Couturier
Walker 
9.18 km
+66 m
-66 m
2h 50
Moderate
Departure from Wy-dit-Joli-Village (Val-d'Oise)
The French Vexin region has numerous megalithic sites dating from the late third millennium B.C. This walk gives you the chance to visit a dolmen in a perfect state of preservation. As you stroll through the fields and woods, you will also be able to see some lovely churches and castles.
Loop around Commeny
Walker 13.37 km
+74 m
-79 m
4h 00
Moderate
Departure from Commeny (Val-d'Oise)
A straight-forward loop around Commeny passing the Perchay and Chaussée Julus Caesar.
Loop departing from Chars
Walker 10.15 km
+104 m
-103 m
3h 10
Easy
Departure from Chars (Val-d'Oise)
Walk starting from Chars SNCF station passing the Château de Saint-Cyr-sur-Chars.
On the way back to Chars there is a narrow pedestrian passage that starts with a staircase.
The Vaucouleurs valley around Dammartin-en-Serves
Walker 11.72 km
+125 m
-124 m
3h 40
Moderate
Departure from Dammartin-en-Serve (Yvelines)
A beautiful walk through stunning and varied landscapes. Historic detours along the way.
Following the Bièvre river through Saint-Quentin-en-Yvelines in Igny
Walker 
19.30 km
+26 m
-121 m
5h 35
Moderate
Departure from Montigny-le-Bretonneux (Yvelines)
The upstream part of this series of three hikes devoted to the Bièvre river. A very pleasant walk along the river and its bodies of water, in a mostly rural setting. A hike from station to station, which can be used to adjust the length depending on the weather conditions or desires of the hikers.
The Roselière (reed beds) of Maincourt
Walker 
9.08 km
+59 m
-67 m
2h 45
Moderate
Departure from Lévis-Saint-Nom (Yvelines)
At the heart of the Chevreuse Valley Natural Park, a hike that allows you to wander through a protected natural site with a trail laid out by the Park. In the Bois de Maincourt, one can see ancient sandstone quarries. The course of the river Yvette, which the trail follows on the way back, finally allows a patrimonial approach with old mills and old washhouses.