Start from the village of Marigny near the church.
(S/E) Walk along the church and cemetery on your left and follow Rue de l'Oratoire (white and redGR® markings).
Then turn left onto Rue des Voituriers.
(1) At the fork, turn right, go through a gate and cross the Bief de la Côte watercourse, keeping to the right at the next fork. Continue to another crossroads.
(2) Turn right again towards the lake shore and follow it until you reach the entrance to the Domaine de Chalain campsite.
(3) Cross the campsite and take the car exit.
(4) At the exit, cross the bridge and immediately take the path on the right, which runs parallel to the paved road for a long time before rejoining it.
(5) Continue right on the paved road that curves away from the lake in a wide left turn.
(6) At the end of the bend, leave the road and take the path that climbs to the left (yellow signpost). Keep left at the next two intersections and you will reach the Belvédère sur la Roche, the first viewpoint over the lake.
(7) Follow the path, ignoring all the paths on the right, and arrive at the second viewpoint, the Belvédère de la Frate.
(8) Continue along the path that slopes to the left, following the departmental road, which leads to the third viewpoint, the Belvédère du Lac.
(9) Join the D90, follow it to the left until the first crossroads.
(10) Turn left and follow the road into the village of Fontenu.
(11) At the statue of the Virgin Mary, turn left and continue straight ahead until you reach the crossroads with a track.
(12) Be careful at this point and take the path that descends straight ahead.
(2) Continue straight ahead and follow the same route in reverse to return to Martigny church and the starting point (S/E).
The signposting in the Jura is top-notch.