The Abbey of Saint-Michel-en-l'Herm dates from 682 AD when it was constructed by Benedictine monks from Noirmoutier. It was destroyed by Vikings in 877 AD. The new church was completed in 1047.
In 1569, Protestants attacked it, killing approximately 200 monks. The motives for the attack are still debated, but one theory is that the attackers sought treasure and manuscripts hidden by the Bishop of Luçon.
The final destruction took place during the French Revolution when the abbey was confiscated and most of buildings destroyed.
The church of the former Franciscan monastery was built probably between 1515 and 1520. It is located in the UNESCO World Heritage Site of Old Rauma. The church stands by the small stream of Raumanjoki (Rauma river).
The exact age of the Church of the Holy Cross is unknown, but it was built to serve as the monastery church of the Rauma Franciscan Friary. The monastery had been established in the early 15th century and a wooden church was built on this location around the year 1420.
The Church of the Holy Cross served the monastery until 1538, when it was abandoned for a hundred years as the Franciscan friary was disbanded in the Swedish Reformation. The church was re-established as a Lutheran church in 1640, when the nearby Church of the Holy Trinity was destroyed by fire.
The choir of the two-aisle grey granite church features medieval murals and frescoes. The white steeple of the church was built in 1816 and has served as a landmark for seafarers.