Circular route through the marshes: Étier de Boulay, Île de Rostu, Kercabellec

A walk through a varied landscape where the marshes tell the story of their distant origins, shaped by the earth and the ocean, with low, undulating vegetation carved out by small streams, and their domestication by man, with salt marshes and oyster beds, not to mention the iconic cabanes à carrelet (fishing huts).

Details

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  • Walking
    Activity: Walking
  • ↔
    Distance: 10.55 km
  • ◔
    Average duration: 3h 05 
  • ▲
    Difficulty: Moderate

  • ⚐
    Back to start: Yes
  • ↗
    Ascent: + 20 m
  • ↘
    Descent: - 20 m

  • ▲
    Highest point: 19 m
  • ▼
    Lowest point: 2 m
  • ⚐ Country: France
  • ⚐
    Area: Brière
  • ⚐ District: Mesquer (44420)
  • ⚑
    Start/End: N 47.391491° / W 2.447012°
  • ❏
    IGN map(s): Ref. 1022OT, 1023OT
  • Hour-by-hour weather

Photos

Description of the walk

Start on the wideGR®34path accessible from the D52 between Mesquer and Saint-Molf. Take the small road on the left towards Trévin, and turn right onto theGR®34. The wide path offers numerous parking spaces over 300 metres.

White and red markings

(S/E) Take the wide path towards Marais la Duchesse and follow it until you reach a fork where you cannot continue along the marsh, which becomes Étier de Boulay.

(1) Turn left onto the slightly uphill path, then right after 200 metres, and finally left to cross the pretty hamlet of Fontaine Bras. Take the first path on the right.

(2) Two alternatives:
- At low tide, at the intersection, leave theGR® which branches off to the left and take the path that runs alongside the Marais la Chouette. Go down the few steps to walk along the Marais Calza before joining theGR®34, which you will take to the right.
- At high tide, continue on theGR®34trail to the left, then take the small road to the right in the hamlet of Rostu.

(3) At low tide, leave theGR® to make a circular route via Île de Rostu. To do this, cross the bridge, then walk along the marsh on the right-hand side of the island. Follow the coastline, entering the enclosure through the gap in the fence, then exit the enclosure. Take the path that follows the marsh as closely as possible on your right until you reach a well-marked path that allows you to complete a circular route by returning to the Île de Rostu while walking alongside the fishing huts.

In any case, continue on theGR® trail that runs along the Notre-Dame la Sauvagère marsh and then the Étier du Goilé until you reach the Kervarin road.

(4) At the intersection, take the opportunity to admire the Port of Kercabellec by taking a 250-metre detour to the right along the small road.
Continue on theGR® via the Kervarin road until you reach the Cap Horniers road.

No signposts

(5) Turn slightly left and follow the D352 to the village of Mesquer.

(6) On leaving Mesquer, turn left onto Rue du Soleil, then left again towards the church on Rue du Midi. Turn right at the Town Hall square onto Avenue de Bretagne, which becomes Rue des Sports as it runs alongside the sports facilities in Mesquer. Pass the Vigne farm, cross the hamlet of Trévin and then Penloc via the Saint-Molf road to return to the starting point (S/E).

Waypoints

  1. S/E : km 0 - alt. 12 m - GR°°®°°34 path accessible from the D52
  2. 1 : km 1.11 - alt. 3 m - GR34
  3. 2 : km 2.07 - alt. 3 m - Path opposite (low tide), on the left (high tide)
  4. 3 : km 3.12 - alt. 4 m - Bridge opposite (low tide), on the left (high tide) - Mès (fleuve)
  5. 4 : km 6.95 - alt. 4 m - GR34 on the left (Kercabellec on the right)
  6. 5 : km 7.91 - alt. 3 m - Keep to the left.
  7. 6 : km 8.94 - alt. 5 m - Rue du Soleil on the left
  8. S/E : km 10.55 - alt. 12 m - GR°°®°°34 path accessible from the D52

Notes

(4) Some sections are not accessible at high tide.

The route includes 2.5 km of asphalt between (5) and (S/E).

Worth a visit

The route:

  • runs alongside the traditional fishing huts on the Étier de la Barre road, which can be accessed from the island of Rostu,
  • provides access to the Port of Kercabellec,
  • offers numerous observation points overlooking the marshes, their vegetation and wildlife (rabbits, deer, numerous birds). There is an observatory between (3) and (4).

Always be cautious and plan ahead when you're outdoors. Visorando and the author of this route cannot be held responsible for any accidents occurring on this route.

The GR® and PR® markings are the intellectual property of the Fédération Française de Randonnée Pédestre.

Reviews and comments

4.5 / 5
Based on 7 reviews

Reliability of the description
4.6 / 5
Ease of following the route
4.6 / 5
Route interest
4.3 / 5
Elviraval
Elviraval

Overall rating : 4.7 / 5

Date of your route : Jul 07, 2025
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★☆ Good
Very busy route : No

A very beautiful hike, at least during the first half between the sea and the marshes. No difficulty.

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kartavan
kartavan

Overall rating : 4.3 / 5

Date of your route : Apr 13, 2025
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★☆ Good
Route interest : ★★★★☆ Good
Very busy route : No

A very pleasant hike, especially in dry weather. Recommended despite the less enjoyable end on the road.

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VISIOPIVOINE
VISIOPIVOINE

Overall rating : 5 / 5

Date of your route : Oct 14, 2024
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.
Avoid during bird nesting season, particularly for plovers, so as not to disturb the wildlife.
No dogs, even on a leash...
Natural area to be protected.

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MF et D
MF et D

Overall rating : 4.7 / 5

Date of your route : Sep 18, 2024
Reliability of the description : ★★★★★ Very good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★☆ Good
Very busy route : No

Route taken at low tide.
A very pleasant and easy hike.
The last few kilometres are along the roadside but with good verges.

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Marie N
Marie N

Overall rating : 4.3 / 5

Date of your route : May 03, 2024
Reliability of the description : ★★★★☆ Good
Ease of following the route : ★★★★☆ Good
Route interest : ★★★★★ Very good
Very busy route : Yes

Very beautiful, varied route through the marshes. Be aware that it may be very wet in places. No particular difficulties.

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Jean-Louis Pinault
Jean-Louis Pinault

Thank you for your comments, which are always valuable.
Kind regards,
Jean-Louis

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eebeaur
eebeaur
• Edited:

Overall rating : 4.3 / 5

Date of your route : Oct 31, 2023
Reliability of the description : ★★★★☆ Good
Ease of following the route : ★★★★★ Very good
Route interest : ★★★★☆ Good
Very busy route : No

The start of the hike is really lovely, although the last 2.5 km are in the town, which isn't as nice. But the start in the marshes is fantastic!
Be aware that part of it was under water, but you can easily walk through a field next to it.

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lespiquet
lespiquet

Overall rating : 4 / 5

Date of your route : Sep 11, 2023
Reliability of the description : ★★★★☆ Good
Ease of following the route : ★★★★☆ Good
Route interest : ★★★★☆ Good
Very busy route : No

A walk in the marshes is very relaxing.

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