The construction of the Canal du Nivernais, in the 18th century, required major improvements. It was necessary to pass by the mountain of La Collancelle and the only means was to bore this one. The walk takes the following 3 tunnels, and you turn around at the hamlet of Port Brûlé: the La Collancelle tunnel (758 m), the Mouas tunnel (268 m) and the Breuilles tunnel (212 m). Between each tunnel are "trenches", the uncovered parts of the channel between the tunnels.