Due to popular piety in earlier centuries, it was part of life in Brittany that everyone who was somehow able to make a great pilgrimage to the seven cathedrals of Brittany, the so-called "founding saints." This was called "Tro Breiz" (Tour of Brittany) in Breton. According to estimates, in the 14th century, up to 40,000 people had to cover a distance of almost 700 kilometers. It is said that if one did not complete the Tro Breiz in one's lifetime, the pilgrimage would continue with the coffin if necessary.
A few years before the turn of the millennium, the "Tro Breiz" was revived – albeit in a different form. In its modern version, the route is spread over seven years, and each year one of the pilgrimage destinations is visited. The seven prominent saints are:
+ Saint Maclovius: Founder of the diocese of Saint-Malo and patron saint of the city.
+ Saint Samson: Founder of the diocese of Dol-de-Bretagne and one of the most famous Breton saints.
+ Saint Briocus: Founder of the diocese of Saint-Brieuc and its monastery.
+ Saint Tugdual: Founder of the diocese of Tréguier and one of the most important saints in Breton history.
+ Saint Paul-Aurelian: Founder of the diocese of Saint-Pol-de-Léon and an important missionary.
+ Saint Corentin: Founder of the diocese of Quimper and one of the most important Breton saints.
+ Saint Hervé: A saint of Brittany mentioned in the Vita Hervei.