The Roman bridge and the forest of Mont

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This hike will take you from the village of Thônes to the village of Les Clefs, following the Fier river and crossing the Roman bridge. The next stop is the Mont forest with its fallen king and new king. You can learn about the history of this king (the tree tadpoles of Thônes) by visiting the website. On your return to Thônes, you can stroll around this village located at the gateway to the Aravis.

Details

n°1370363
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  • Walking
    Activity: Walking
  • ↔
    Distance: 9.82 km
  • ◔
    Average duration: 4h 05 
  • ▲
    Difficulty: Moderate
  • ⚐
    Back to start: Yes
  • ↗
    Ascent: + 435 m
  • ↘
    Descent: - 430 m
  • ▲
    Highest point: 1,019 m
  • ▼
    Lowest point: 619 m
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Description of the walk

Head to the car park located on the banks of the Fier, on the left just after the village hall and the bridge, coming from the town centre.

(S/E) Take the path that runs alongside the Fier towards the "Les Mésanges" lodge. Follow this path to the next road at Pont de Chamossière.

(1) Take this road uphill to the right, then the Chemin du Carré on the left.

(2) At the first hairpin bend, take the path on the left, which is closed to horses, and which descends towards the Fier a little further on. Cross the path leading to the houses and continue straight ahead along the Fier to reach the road leading to Pecherat.
Cross the bridge on the left and take the road on the left to reach the Roman bridge.

(3) Then retrace your steps to find the D12 and follow it to the left until you reach a steep path on the left.

(4) Take this path, which climbs up to the village of Les Clefs and arrives at the cemetery. Follow the road that passes between the church and the town hall/school to a car park on the left. At the end of the car park, near the transformer, take the steeply descending path. At the bottom of the path, cross the bridge and take the road on the right and the path going up opposite, until you reach the road serving a few houses.

(5) Follow this road and cross the D16 to take the Route des Pohets opposite. Then take the Route des Galfas, keeping to the left.

(6) After a large farm, about 350 metres into a hairpin bend, take the path on the left. Follow this path until you reach a fork with directional signs. Take the path on the right towards the Mont forest. After about 200 metres, take the path that climbs steeply to the right. Follow the path carefully and do not be distracted by the logging "trenches".

(7) At the top of this path, continue on the first path on the left (north), towards the Roi du Mont. After the old paragliding take-off area (flat, open area with a superb view of Thônes and Mont Lachat).

(8) Follow the path on the left which leads back to Thônes. (Just before taking this path, you can visit the Roi du Mont.)

(9) At the end of the path, continue downhill on the road. Cross the street towards the church.

(10) Cross the square towards the pharmacy. Walk along both sides of the museum-media library. Cross the square lengthwise towards the village hall. Walk along the side of the village hall to reach the bridge and the car park at the starting point (S/E).

Waypoints

  1. S/E : km 0 - alt. 623 m - Car park after the village hall and the bridge at - Fier (rivière)
  2. 1 : km 1.31 - alt. 645 m - Chamossière Bridge
  3. 2 : km 1.66 - alt. 675 m - Path "no horses allowed"
  4. 3 : km 2.81 - alt. 666 m - Pont Romain (Les Clefs)
  5. 4 : km 2.96 - alt. 668 m - Ascent to the village of Les Clefs
  6. 5 : km 3.65 - alt. 731 m - Exit the undergrowth onto a tarmac road
  7. 6 : km 4.75 - alt. 848 m - Path in a hairpin bend on the Route des Galéas
  8. 7 : km 5.84 - alt. 1,012 m - Towards Roi du Mont
  9. 8 : km 7.07 - alt. 976 m - Le Roi du Mont
  10. 9 : km 9.08 - alt. 647 m - Return to the town centre
  11. 10 : km 9.48 - alt. 622 m - Église Saint-Maurice (Thônes)
  12. S/E : km 9.82 - alt. 623 m - Car park at the start. Confluence of the Fier and - Nom (torrent) - Affluent du Fier

Notes

Given the proximity of the Fier river and the streams that flow into it, the first part of this walk can be muddy in wet weather.

Worth a visit

The Roman bridge
The village of Les Clefs
The King(s) of Mont
Thônes.

Reviews and comments

4.3 / 5
Based on 10 reviews
Reliability of the description
4.4 / 5
Ease of following the route
4.4 / 5
Route interest
4.1 / 5
sergiomont
sergiomont

Overall rating : 4 / 5

Date of your route : Jan 15, 2026
Reliability of the description : ★★★★☆ Good
Ease of following the route : ★★★★☆ Good
Route interest : ★★★★☆ Good
Very busy route : No

It's a shame the route was in the shade.
It wasn't very warm.
Good route.

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sergiomont
sergiomont

Overall rating : 4 / 5

Date of your route : Jan 05, 2026
Reliability of the description : ★★★★☆ Good
Ease of following the route : ★★★★☆ Good
Route interest : ★★★★☆ Good
Very busy route : No

Hello,
We went on the hike on 2 January.
There wasn't much sun that day.
The hike is short but good.
A little slippery because of the frost and dead leaves.
We climbed 550 metres.

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sergiomont
sergiomont

Overall rating : 4 / 5

Date of your route : Jan 05, 2026
Reliability of the description : ★★★★☆ Good
Ease of following the route : ★★★★☆ Good
Route interest : ★★★★☆ Good
Very busy route : No

Hello,
We went on the hike on 2 January.
The hike is short but good.
A little slippery due to frost and dead leaves.
We climbed 550 metres.

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ldominique 66420
ldominique 66420

Overall rating : 4.7 / 5

Date of your route : Aug 18, 2025
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★☆ Good
Very busy route : No

A pleasant hike along the banks of the Fier river and across the Roman bridge.
The end of the trail in the forest is a bit monotonous

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User 18390606

Overall rating : 4.7 / 5

Date of your route : Jul 15, 2025
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★☆ Good
Very busy route : No

Halfway along the route, we stopped for refreshments and enjoyed some delicious homemade ice cream at Lait'able des Frangins in the village of Les Clefs. The return trip along the Fier river was very pleasant!

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Jean-luca
Jean-luca

Overall rating : 4 / 5

Date of your route : Nov 22, 2024
Reliability of the description : ★★★★☆ Good
Ease of following the route : ★★★★☆ Good
Route interest : ★★★★☆ Good
Very busy route : No

Lovely family walk.

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Yolande T
Yolande T

I disagree with the term "uninteresting": beautiful mountain views and enjoyable walks along the river. It all depends on what you are looking for.

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JOSETTE25
JOSETTE25

Overall rating : 3.7 / 5

Date of your route : Jul 31, 2022
Reliability of the description : ★★★★☆ Good
Ease of following the route : ★★★★☆ Good
Route interest : ★★★☆☆ Average
Very busy route : No

Hike done in reverse. Shady section, which is welcome in this hot weather. Not much of interest, except for the Roman bridge at the end of the route.

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Yolande T
Yolande T

Overall rating : 4.7 / 5

Date of your route : May 20, 2021
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★☆ Good
Route interest : ★★★★★ Very good
Very busy route : No

The only sunny day after days of rain. So we did the hike in reverse, which was fortunate because the forest trail would have been slippery on the way down. What's more, when you come out of the forest, the view is more beautiful at the back of La Tournette and the chalets scattered along the road to the Col du Marais.
We enjoyed the two picnic tables in the square at Les Clefs, plus a covered area in case of rain.
A beautiful route back along the banks of the Fier. A beautiful waterfall behind the old sawmill.
A very beautiful hike.

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LAFOND74
LAFOND74

Overall rating : 4.7 / 5

Date of your route : May 09, 2021
Reliability of the description : ★★★★☆ Good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★★ Very good
Very busy route : No

A beautiful hike best enjoyed in good weather as it is very shaded. I did it in the opposite direction to the one suggested, which I think is better as you start with the uphill climb and finish with a stroll along the Fier.

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Jumbalaya
Jumbalaya

Overall rating : 4.7 / 5

Date of your route : Sep 19, 2019
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★☆ Good

Good evening
Part of the route is completely overgrown with plants, fortunately not nettles, between Les Clefs (path to the left of the transformer) and the arrival at the D16. Also worth noting is that the route is blocked at point 4: the path that climbs to the left at Les Clefs on the D12. We took it anyway because we didn't want to climb up to Les Clefs via the road. However, this should not be done on windy days due to fallen trees.

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Netra
Netra ★

Hello Katy, and thank you for this useful information!

So we'll have to wait until it reopens...

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katy_2578
katy_2578

The hiking trail is blocked at the bottom of La Clef due to bad weather. What a shame! No date has been set for the trail to reopen. It is impossible to continue.

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