A challenging loop connecting the villages of vallon du Truison.
A consistant ascent of the small valley by "Les Envers" till Sainte-Marie-d'Alvey, a panoramic ascent on the GR9 till Saint-Maurice's plateau before a descent towards Grésin and then Champagneux. Easy ending on the Viarhôna and paths in the plains of Rhône and along the Guiers river.