The Rocher du Long Boyau and the Gorges du Houx

From the Ermitage de Franchard, this is a very varied hike which will take you past old sandstone quarries, the Gorges du Houx and the charming Mare aux Pigeons. On the route are several vast viewing points, numerous spectacular rocks and the curious Grotte du Serment cave.

N.B. The elevation and the time shown appear to be under-estimated: count on about 250 meters and 4 hours of walking.

Technical sheet No. 4098826

A Fontainebleau walk posted on 27/02/16 by djhoward. Last update : 04/09/20
Calculated time Calculated time: 3h05 ?
Distance Distance : 10.02 km
Vertical gain Vertical gain : 74 m
Vertical drop Vertical drop : 75 m
Highest point Highest point : 139 m
Lowest point Lowest point : 88 m
Moderate Difficulty : Moderate
Back to starting point Back to starting point : Yes
Walking Walking
Area Area : Forest of Fontainebleau
Location Location : Fontainebleau (77300)
Starting point Starting point : N 48.408985° / E 2.634734°
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Rock art?


Start point: Car park of the Ermitage de Franchard.
Access: The car park is located a few meters from a crossroads adorned by a cross on the D301, the so-called Route Ronde (signpost). This crossroads is close to a crossing on the Route Ronde with the D409 which connects Arbonne-la-Forêt and Fontainebleau (when you come to this crossing, turn right).

No markers

(D) At the end of the car park (west), take the alley that leads to the Hermitage (signposted - Ermitage). Go past a sign "Promenade de Franchard". Get to a signpost "Arbor&sens" (the Hermitage fountain is located just behind).

Red and white + green and white markers

Follow the sign "Arbor&sens" and go fully south on the Route de Tavannes, which is a good sandy path. At a fork, take the left-hand path. After a bend to the right, you'll see additional blue markers. Reach the entrance to the site "Arbor&sens" (wire fence).

Markers: Blue + blue marks designated by letters

(1) Turn left (east) on the Route des Gorges de Franchard and follow the trail Denecourt-Colinet No. 7. At the first intersection, at the end between forest plots Nos. 762 and 768, turn left on the Route des Ermites. At the fork which appears immediately (2 pine trees between which are markers), leave the markers momentarily and take the trail on the left. You'll soon reach the Mare aux Pigeons (signpost).

(2) Retrace your steps and at the fork find the markers, turning left on the Route des Ermites. About 50 meters further on, shortly after a sign "Route des Ermites" high up on a pine tree to the left, leave the path and turn right between two small rocks.
N.B. Be vigilant here, the markers aren't very visible because they are quite old: markers on the ground indicate the right-hand turn, a marker is located on one of the two small rocks that you go between (the left) and, if you go past this fork, there is a cross at eye level on a rock to your left. If you encounter a red and white marker (GR), turn back.
Walk through ferns and pass a rock indicated by a blue star on the right. At a T-junction, turn right (southeast) on the trail No. 7-8 (link between Nos. 7 and 8). Reach the Route Ronde (route D301) and the cross it (carefully).

(3) Continue southeast on a poorly marked trail that starts between the Route des Gorges de Franchard on the left and the Chêne Rouge on your right (signposted Denecourt-Colinet) and begin to descend slightly. Follow the Route du Sommet remaining in an east-southeast direction (on the few signs that you see, follow the direction of the Route de Froidour) and ignore the paths leading off on either side. Walk past the old sandstone quarries on the right, easily identifiable by the quarry face, and through pleasant, mossy undergrowth. After plot No. 121, stay on the ridge with a steep slope on your left hand side.

(4) After a left-hand turn between rocks, find a fork with a signpost to Denecourt-Colinet on a tree: follow trail No. 8 to the right (the trail on the left descends steeply). A little further, skew right and climb up to a peak in clear view mounted by a single pine tree (neither the map nor diagram are accurate at this location). Reach the large Long Boyau viewing point Go beyond this peak in a southeast direction and down between the rocks (be careful, the markers here are mostly on the ground). Lower down at a fork, take the trail on the left and pass a row of rocks. Go past the H shelter, to rock G and veer to the right. At a fork, take the trail on the right and enter a maze of rocks.

Cross the Route Henriquez, continue opposite and turn immediately right. Climb the maze of rocks. Pass under a rock with a blue star and then turn left. Pass rock B on your right. Further on, weave down between the rocks and come out into a more open space. Reach the Route de Froidour and make a quick left-right dogleg to cross it. Climb a few meters and then descend further down to an signpost to Denecourt-Colinet.

(5) Turn right in the direction of Long Boyau / Carrefour de la Libération. Climb up and when you get to a fork, follow the trail on the right. Continue to climb through the ferns and mossy rocks. At rock H, veer to the right and at the next fork, take the left-hand trail. After a signpost "Route du Polygon", veer left. Weave along and further on, turn right towards a large block. Circumvent this block (G) on the right-hand side and weave upwards. Pass under rock F (called Arche d'Alliance) and then descend. Climb back up, skew left and climb the side of the slope. Then turn sharply right towards a peak, keeping to the right (the markers are less frequent on this climb). Come out on the Bombarde viewing point, a wide space at the top of the rocks where there is a solitary pine tree.

(6) Go slightly back on yourself to find the D marker on the ground: squeeze through the crack on the right. Descend and weave between the blocks. Cross a steep trail. Climb up, keeping to the left. Turn right and weave down. Cross another perpendicular trail and climb back up twisting between the rocks (you'll need to use your hands on a few occasions). After rock B, walk along almost flat terrain. When the trail reaches two small ruined buildings (an old practice target area observatory), turn left and weave down along a well marked trail. Pass under the rock A (called the Porte de Pierre le Grand) and come out on the Route du Treillage (plot No. 113 on the pine tree opposite).

No markings

(7) Leave the Denecourt-Colinet trail, continue opposite and turn left (northwest). Take this good sandy path until the Carrefour de l'Emerillon. At this intersection, go fully north on the Route du Mont Fessas that starts just to the right of an isolated block of rocks and between two trees each bearing plot No. 114. Go straight ahead and get to the Carrefour du Mont Fessas.

Markers: Blue + blue marks designated by letters

(8) Take the 2nd trail to the left, which is poorly marked and starts just to the right of the Route du Mont Aigu. Go east on almost-flat terrain. The trail rises gently and bends to the right to climb Mont Aigu in a spiral. Do almost three-quarters of a circle on a gentle slope and, at a fork, turn right. At rock Q, turn left and get to rock P (called the Cachalot).

(9) Circumvent this rock to the left and summit of Mont Aigu. Start the descent and follow a sweeping arc in a clockwise direction. Cross the Route du Mont Aigu coming from the left, go a few meters on this road and then leave it, turning right between the plot Nos. 114 and 110 and continue opposite on trail no. 8. As you approach top of a small hill, keep left and reach a large shelter below to your right, bearing the inscription "DFD 1853" on the entrance.

(10) Take the stairs down into the shelter and cross it fully going left-right (the shelter is rather long but sufficiently well- lit). As you exit the shelter, turn left, go over a rock and take a hairpin turn to your right. Ignore the rock to your right and walk on almost flat terrain with a slope on the left-hand side. At a fork, continue on trail No. 8 to your right (ignore trail no. 8-8 coming from the left) and descend in a northwest direction until the Carrefour du Mont Aigu (signposted "Route de l'Emerillon").

Take the third path on the right (the first being very poorly marked), meaning the first that climbs. At the top of the hill, go around a block via the right-hand-side. Leave rock G to the right and then rock F To the left. At a fork (the marker is on a stump), follow the left-hand trail and crawl under rock E (called Antre de Judith). At a fork, go left. Turn right and crawl (which is the right word!) under rock C. When you come out, continue opposite and then keep right to reach a signpost to Denecourt-Colinet.
N.B. If you don't want to crawl under the rock, you can go around it to the left and then switch right in the direction of the signpost which is clearly visible.

At the signpost (T-junction), turn left in the direction of Franchard-Ermitage. After walking between the rocks, cross the Route du Lance taking a short left-right dogleg and continue on a trail with few markers. Bypass a large block (F) to the left and find another signpost to Denecourt-Colinet.
N.B. Here, the blue line on the map seems to show that the trail No. 8 cross the Franchière intersection, which is incorrect: the trail avoids this intersection and passes slightly further north.

At the sign, go right on the trail No. 7-8 in the direction of Franchard. Climb slightly and then turn right towards rock D. At this rock, take a hairpin left and go over another rock. Weave and then walk northwest along the slope. After a right-hand turn, go left around a block of rocks, spot marker A above and continue, bending round to the left.
N.B. The "official" marker invites you to circumvent this block to the right and to go almost right the way round passing under overhangs: you don't have to....

Weave down in zizags. When you get to the bottom, at a T-junction, turn left. At the next intersection turn right (markers on the ground). Climb up to a small peak mounted by rocks in the form of menhirs. Start the descent and join the GR1E coming from the right.

Red and white + blue markers

Turn left on the GR and descend. At the bottom, at a T-junction, turn right and come immediately to an intersection.

Red and White Markers

(11) Leave the blue markers to the right and continue opposite on the GR, on the Route du Mont Aigu in the direction of the D301 (sign). Walk along a false flat on a good path through a pine forest. Cross the Route Jean, continue west and gently climb the Gorges du Houx. After a right-hand turn, you come to Carrefour du Houx (which is sandy).

Red and white + blue markers

Take the second road on the left, the Route de la Gorge du Houx, still towards the D301. Cross the Route Mazarin and, after a forest barrier, cross the Route Ronde (D301, carefully). Continue on the road to the Mare aux Pigeons.

Red and White Markers

After less than a hundred metres, at a fork, ignore the trail marked in blue that goes off to the left (towards a point you took on the outward leg) and continue on the GR. Cross the Route du Monastère. At the next T-junction, turn right. Soon there isn't really a trail: walk north and then northwest between the pine trees on rock or sand, identifying the markers. After having crossed a path, turn right on a wooden staircase (the GR route is incorrect here). N.B. There are two staircases, take the one to the west. At the top of the stairs you'll immediately find the car park (D/A).

Waypoints :
D/A : km 0 - alt. 139 m
1 : km 0.66 - alt. 135 m - Route de Tavanes x Route des Gorges de Franchard
2 : km 1.05 - alt. 135 m - Mare aux Pigeons
3 : km 1.52 - alt. 136 m - Route Ronde
4 : km 3 - alt. 118 m - Junction: trail Nos. 7-8 and 8
5 : km 3.63 - alt. 104 m - Route du Polygone
6 : km 4.22 - alt. 115 m - The Bombarde viewing point
7 : km 4.73 - alt. 93 m - Route du Treillage
8 : km 5.47 - alt. 95 m - Carrefour du Mont Fessas
9 : km 6.12 - alt. 122 m - Mont Aigu - Le Cachalot
10 : km 6.7 - alt. 113 m - Grotte du Serment
11 : km 8.49 - alt. 112 m - Intersection
D/A : km 10.02 - alt. 139 m

Useful Information

Terrain and difficulty:
On the Denecourt-Colinet trail (blue markers), there are numerous sections where you have to squeeze between rocks or go under rocks, getting on the ground more or less. On a few portions of these trails, you walk on rock that is flush with the ground: it's therefore advisable to wear shoes with a good grip.

variants and possible combinations:
- In fair weather, the Franchard site is very popular: Do'nt hesitate to arrive early. An alternative is offered at the crossroads of the Route Ronde (D301) but the amount of space there is limited.
- If at the end of the walk, if you haven't had enough of weaving between rocks, there is an additional section on the Platières du Houx. At the crossroads(11), keep following the blue markers and follow trail No. 7-8 northwest. At an intersection, go left, remaining on trail No. 7-8. Then go east, on sections alternating between rock flush with the ground, and sand.
- This hike can be combined with the hike "The Gorges de Franchard and the Antre des Druides", published on Visorando and which has the same starting point. Count on about 6 to 7 hours of walking, and classify all of it as "difficult".

No marked water filling points. Shelter at the Grotte du Serment(10).
Lots of potential locations for a picnic: the Mare aux Pigeons(2), all the viewing points, ...

Markers and orientation:
- The blue markers are displayed in a variety of ways: high trees, rocks at eye level, rocks on the ground, ... Although it is very dense, be careful not to lose sight of these markers.
- At intersections, the names of paths are generally signposted at tree height.
- Despite the markers and signs, a 1/25000 map is necessary (at least the one available with this description). A compass isn't very heavy can be very helpful.

Visorando and this author cannot be held responsible in the case of accidents or problems occuring on this walk.

During the walk or to do/see around

In Franchard, between (D/A) and:
- The Ancien ermitage de Franchard, the presence of hermits being evident from the 11th century.
- Puits de Franchard (wells) (early 19th century).
- Fontaine des Ermites (12th century).

On the route:
- Lots of spectacularly shaped rocks.
- The Mare aux Pigeons (pond) (2).
- The old sandstone quarries, between (3) and(4).
- The viewing points: Large viewing point of the Long Boyau after(4) ; The Bombarde viewing point (in reference to the nearby firing range)(6) ; Mont Aigu ; ...
- After(4), the ruins of the firing range observatory on the "Polygone" located to the south of the Rocher du Long Boyau. This space was used by the École d’application de l’artillerie et du génie (military and engineering school) which was set up in Fontainebleau in 1870 (a certain Alfred Dreyfus was second lieutenant from 1880 to 1882).
- The Grotte du Serment cave (10). The large shelter that Charles-François Denecourt (1788-1875, creator of the trails that bear his name today) was built between natural rocks.
Having already spent much of its time and money on various tourist facilities in the forest of Fontainbleau, he promised that this would be the last. The inscription "DFD 1853" on the entrance refers to the date the shelter was built, the acronym stands for "Dernière Folie de Denecourt" (The last madness of Denecourt"). It should be noted that you can find the Grotte du Parjure on another trail...

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The GPS track and description are the property of the author.