In 1008, Geoffrey I, Duke of Brittany, died and gave by his will the southern half of the island of Arz to the Abbey of St Gildas de Rhuys. He assigned a few peasants to start developing and cultivating the soil. Construction of the priory of Notre Dame was started in 1034 by monks seconded from the Abbey of St Gildas de Rhuys. Construction of the church of Notre Dame next to the priory was subsequently launched to serve the whole island, and was completed in 1412. In 1514, an agreement further made it official that this church was to fully serve both the southern and northern parts of the island. To this day, regular services are still held in the church. The priory of Notre Dame was acquired and renovated by the municipality in 1970 and now serves as both the town hall and school for the island.