Starting from the car park of the craftsmen's house, this circuit goes around the Saint Michel reservoir. After a first part on track and road, you reach the Nestavel dam, at the foot of the Brennilis power station. From there, the route follows the lake along two kilometres before going around the Vénec nature reserve and continuing through the moors. A succession of wooden footbridges mark out the route to complete the loop and return to Ty Blaise and finally to the starting point.

Warning : In order to limit the impact of the marking signs, this route is not specifically marked out trail. Follow the yellow hiking marking signs "Circuit du Yeun".