Sentier du Syl au Trou Bleu trail

The trail starts at the port of Lavau-sur-Loire and takes you to the Observatory with a magnificent view of the marshes and the Loire. The walk then continues to the Étangs du Trou Bleu, a former blue granite quarry. Next, enjoy a country walk to the Fresnier marsh with its canals populated by storks.

Details

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  • Walking
    Activity: Walking
  • ↔
    Distance: 14.98 km
  • ◔
    Average duration: 4h 20 
  • ▲
    Difficulty: Moderate

  • ⚐
    Back to start: Yes
  • ↗
    Ascent: + 11 m
  • ↘
    Descent: - 12 m

  • ▲
    Highest point: 15 m
  • ▼
    Lowest point: 2 m

Photos

Description of the walk

Departure from the car park at the port of Lavau sur Loire.

(S/E) From the car park, turn right, heading south-west.

(1) Turn onto thefirst path on the left and follow it to the observatory. About 200 metres before the observatory, there is a pontoon where you can observe the marshes.

(2) Feel free to climb up. There is a superb view of the marshes and the Loire River from the top of the observatory. Retrace your steps for a few dozen metres, then take the path on your left. Follow it and turn left at the first intersection towards the Étangs du Trou Bleu.

(3) Go around the ponds on the left, then cross the road towards the hamlet of Le Legas. At the entrance to the hamlet, take the path on your left. Ignore the paths on the right or left and continue to La Pélarderie and a T-junction.

(4) Take the road on the left for about 300 metres towards Les Noëls, then turn right onto the path. At the end of the path, turn left towards Le Vigneau, then continue straight on for 500 metres. Turn right towards La Bergerie.

(5) Cross the D3 road and take the Chemin de l'Orme for 300 metres. Take the path on your left.
After a few hundred metres, ignore the path that branches off to the left and continue straight ahead for about 200 metres. You will enter the Marais du Fresnier.

(6) Turn slightly left and take the path that goes straight ahead for 1.5 km towards the east. At the end of the path, turn right and join the road at a T-junction.

(7) Take the road on the left towards Les Coudelières. After a few hundred metres, you will come to a path. Take it on the right for a few dozen metres to reach the Sentier du Syl au Trou Bleu.

(8) Turn right. You will soon reach the road. Follow it to the left until you reach La Close. Continue right on the D90 until you reach the crossroads with a farm building on your left at a place called La Noë Chénier.

(9) Leave the D90 on the left and turn onto the dirt track. Follow this to the hamlet of Le Pavillon, then rejoin the D90.

(10) Turn left, then immediately left onto Chemin de la Goupillais. A few hundred metres further on, cross the bridge over the Étier du Syl, turn right to follow its bank straight ahead and return to the car park at the port of Laveau (S/E).

Waypoints

  1. S/E : km 0 - alt. 4 m - Port de Lavau
  2. 1 : km 0.23 - alt. 4 m - The Lavau marshes
  3. 2 : km 1.41 - alt. 3 m - The Observatory - La Loire
  4. 3 : km 2.85 - alt. 6 m - Trou Bleu ponds
  5. 4 : km 5.68 - alt. 5 m - La Pélarderie
  6. 5 : km 7.49 - alt. 5 m - La Bergerie
  7. 6 : km 8.37 - alt. 3 m - Fresnier Marsh
  8. 7 : km 10.25 - alt. 3 m - Les Coudelières
  9. 8 : km 11.02 - alt. 3 m - Sentier du Syl au Trou Bleu trail
  10. 9 : km 12.36 - alt. 4 m - La Noë Chénier
  11. 10 : km 13.6 - alt. 6 m - D90 - La Goupillais
  12. S/E : km 14.98 - alt. 3 m - Lavau harbour car park

Reviews and comments

4.7 / 5
Based on 18 reviews

Reliability of the description
4.7 / 5
Ease of following the route
4.8 / 5
Route interest
4.6 / 5
Crandonnée
Crandonnée

Overall rating : 4.7 / 5

Date of your route : Dec 08, 2025
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★☆ Good
Route interest : ★★★★★ Very good
Very busy route : No

Reconnaissance carried out in the rain. Difficult access, muddy paths due to ruts made by tractors.

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User 24338531

Overall rating : 4.7 / 5

Date of your route : Sep 30, 2025
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★☆ Good
Very busy route : No

A very pleasant hike, especially at the end of September, with varied landscapes and paths. It's a shame that the starting point has been diverted due to the poor condition of the footbridge leading to the observatory.
We recommend this hike, preferably in autumn or spring to avoid the heat and crowds of summer.

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bigjim
bigjim

Overall rating : 4 / 5

Date of your route : May 12, 2025
Reliability of the description : ★★★★☆ Good
Ease of following the route : ★★★★☆ Good
Route interest : ★★★★☆ Good
Very busy route : No

Nice circuit, pleasant starting point. Best done outside of winter...

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bikeràpied
bikeràpied

Overall rating : 4.7 / 5

Date of your route : Sep 08, 2024
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★☆ Good
Very busy route : No

Good signage, storks, herons and a mother raccoon with her cubs.
Lovely facilities for observing all this.
What more could you ask for?
We were delighted.
Be careful, in wet weather, the planks leading to the first observatory are very slippery.

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Alex27
Alex27

Overall rating : 4.7 / 5

Date of your route : Aug 25, 2024
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★☆ Good
Very busy route : No

It was a good hike. More like 16 km.
It starts off very well with the observatory and the Trou Bleu pond. However, it then continues along long straight stretches where there isn't much to see. At the end, there is a magnificent walk through the marshes where you can see lots of animals (storks). Once you leave the marshes, you're back on long straight stretches (grass paths surrounded by trees).
A very beautiful walk, but quite long.
One small downside: there are no picnic tables along the 16 km route. The benches are at the start and end. We had our picnic on the grass at a crossroads. It's a shame.

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Javaux celine
Javaux celine

Overall rating : 4.3 / 5

Date of your route : Jun 09, 2024
Reliability of the description : ★★★★☆ Good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★☆ Good
Very busy route : No

Lack of maintenance of grass paths

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pierre.nassif
pierre.nassif

Overall rating : 5 / 5

Date of your route : Jul 20, 2023
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★★ Very good
Very busy route : No

A very beautiful, varied hike with magnificent scenery.
Very few people (in July and during the week)

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Pan
Pan

Overall rating : 5 / 5

Date of your route : Jul 09, 2023
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★★ Very good
Very busy route : No

A very beautiful hike with varied landscapes (wooded countryside, marshes) and numerous birds, including a pair of storks with their young that we observed.

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ceraco@free.fr
ceraco@free.fr

Overall rating : 5 / 5

Date of your route : Jun 26, 2023
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★★ Very good
Very busy route : No

A lovely walk, and I spent the night in my motorhome at the beautiful starting point by the water.

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Le Lany
Le Lany

Overall rating : 5 / 5

Date of your route : Jun 20, 2023
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★★ Very good
Very busy route : No

A very pleasant route between the banks of the Loire and the marshes, with a special mention for the starting point

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Jp9374
Jp9374

Overall rating : 4.7 / 5

Date of your route : Sep 08, 2022
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★☆ Good
Very busy route : No

A peaceful hike where you pass from marshes to hedgerows.

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eugene.mil
eugene.mil

Overall rating : 5 / 5

Date of your route : Apr 18, 2022
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★★ Very good
Very busy route : No

Route to be taken during dry periods due to risk of water in the marsh

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agi
agi

Well, yes. It's not just hikers, there are also people who work in the countryside...

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LV
LV

The only downside: on Chemin de la Goupillais, we came across a tractor with a large trailer perpendicular to our route, forcing us to take off our backpacks and squeeze sideways between the tractor's wheel and the barbed wire fence. The same thing happened 2 metres further on, where a tractor with a large machine was blocking the route, even though it was marked in yellow. Fortunately, there were only three of us; I can't imagine what it would have been like with a large group!

On the other hand, there were some very beautiful and varied landscapes with nice picnic areas.

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AG
AG
• Edited:

Overall rating : 5 / 5

Date of your route : Sep 26, 2021
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★★ Very good
Very busy route : No

Very beautiful route. Varied landscapes: bocage, marshes, banks of the Loire, bird observatories.
Very reliable signposting. Shortcuts possible

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