Park at the Source de l'Yonne car park at a place called "Port des Lamberts", about 1.5 km north-west of Glux-en-Glenne via the D300.
(S/E) Head south, cross the D300, follow it towards Glux until you reach a wooden structure marking the Source de l'Yonne, with information boards. Take the signposted path that descends just after this structure. You will reach boardwalk paths to cross the peat bog area. Continue along a good forest track. A little further up, it joins a forest path which you follow southwards to the Source de l’Yonne
(1) Take the well-maintained forest path on the right (follow the markings symbolised by two hands holding a divining rod with two branches). Pass a house, and 50 m further on, turn right onto the forest track which climbs steeply up the slope. You’ll reach a pass at the junction of several paths. The path marked on the map is no longer visible; head northwards, staying on the ridge line until you reach the summit of Mont Preneley.
(2) From the summit, descend roughly westwards then southwards down the steepest slope. Choose the easiest route through a very open forest with no undergrowth until you reach a good forest track (coming from the Col du Haut Mathelin). Take this track to the right, heading north-west to the hamlet of Les Vaillants, where you will find a good forest road. Take this to the left and continue to the D27.
(3) Follow the D27 to the right for about 1 km until you reach a junction with the D197. Turn left for a few metres onto the small road which joins a local road; take this to the left, heading due south. Cut across the right-hand bend via the shortcut and cross over to the opposite side to pass through the hamlet of Carré de la Rose. Continue on thePR® to Rangère.
(4) At the T-junction in the hamlet, turn right, cross the woods and then, at the right-hand bend, leave the road via the path on the left signposted “Rangère dam”. Cross the dam, reach a road, turn left for about 150 m and then turn right onto a path that climbs a gully heading south-southeast. Cross the D27 and reach the D18.
(5) Follow it to the left for a few metres and immediately turn left onto the grassy path that climbs the slope at a right angle. At the crossroads, turn right, then left between the two houses. Continue climbing the hillside for about 1 km.
(6) At the junction with a good forest track, take the track on the right (orange markings) which runs alongside the forest track. Continue to the hamlet of Anvers, reaching the D500 (cross at the junction on the right).
(7) Follow the D500 to the left. After the right-hand bend, at the junction in the next hamlet, take the path leading down to the right, following the orange markings. You will reach an isolated house at the bottom of a valley: Les Cléments.
(8) Continue to the right until you reach the junction with theGR®13: please note that the signposted path crosses theGR® further south and lower down than indicated on the IGN map.
(9) Take theGR® to the left and head north; the path joins the D300. Follow it to the left along a wide right-hand bend to the village of Glux-en-Glenne. Continue to the junction opposite the church.
(10) Keep the church on your right and head up through the village on the D500 towards “Haut Folin”. After leaving the village, take the path on the left 100 m before the crossroads. Join the D300 and follow it for just over 1 km, until you reach a crossroads with forest tracks, situated almost at the pass.
(11) Turn left, and immediately at the fork, take the right-hand branch. You will arrive at the archaeological site of the source of the Yonne, signposted on the right.
(12) Return to the path and continue to the Source de l'Yonne.
(1) Then retrace your steps along the path you took on the way there. Be careful and stay alert! You will need to veer right several times, following the signposting marked by two hands holding a diviner’s fork. Return to the car park.
From the car park, treat yourself to the short walk “the Yonne waterfalls” to the Saut de la Perche.
(13) and back (S/E).