Mont Saint-Michel

In the 4th century, when Christianity appeared in Armorica, a chapel dedicated to St. Stephen, the first Christian martyr, was erected on the island.

An excerpt from the article 22 facts about Mont Saint-Michel
Later, a chapel appeared at the foot of the rock in honor of St. Synphorian, the first martyr of the Gauls. There were also hermitages there, which these chapels took care of.