According to the Celtic legend, Hélène, King Hoël's daughter, was kidnapped by a giant and held on the rocky island situated in the heart of Mont Saint Michel bay, where she was later buried. This is where the name "Tomberlaine" comes from (Tomb of Hélène).
This granite island which can be reached only at low tide was a refuge for hermits in the Middle Ages. In the 11th century a priory was built here. Monks from Mont Saint Michel then built a manorhouse the ruins of which can still be seen today. During the Hundred Year War, an English garrison based on the island built ramparts to protect them from French knights from Mont Saint Michel.
Today Tomberlaine is a bird sanctuary, home to numerous species of marine birds and seals.