The Lock trail

Start from the Tête de Chien in Olonne-sur-Mer forest.

1. Depart from the car park and follow the Tête de Chien path. After 1.8 km, turn right. Visit the wooded dune: this is a relatively recent forest: slightly over 170 years old. It is in fact planted with trees in order to prevent the progress of the sand into the low-lying marsh areas, or even into some small villages. It is mainly planted with maritime pines and holm oak (not to be confused with holly!). The National Forestry Office, which manages this forest, is carrying out many tests. The aim is to find trees which are able to survive in the salty air and the poor and salty soil which has a high lime content owing to the large number of shells in the sand. During your outing, you will see maple, robinia, and black pine from Corsica. You will pass through a zone planted with robinia (white blossom in May) at the foot of which in the spring, you will find: wild hyacinths, grape hyacinths, and arum lilies, and in the summer: rockrose and stinking iris. Caution: for several hundred metres before the lock, you will share the route with the coastal cycle path.

2. Arrive at Gachère Lock: it regulates the water level in the surrounding marshes. The lock openings are announced in the press under the section "water movements" Two waterways empty into the sea at this lock: the Vertonne and the Auzance. On the other side of the lock, you are in the commune of Brétignolles.

3. Make your way to Granges beach: this beach is supervised in the summer. You will see many stones with holes in them: a shellfish, the piddock, spends its life carving its gallery out of the tender rock.

4. Walk about 800 m before returning to the dune and passing through the forest again back to where you started.