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.
Visby Cathedral (also known as St. Mary’s Church) is the only survived medieval church in Visby. It was originally built for German merchants and inaugurated in 1225. Around the year 1350 the church was enlarged and converted into a basilica. The two-storey magazine was also added then above the nave as a warehouse for merchants.
Following the Reformation, the church was transformed into a parish church for the town of Visby. All other churches were abandoned. Shortly after the Reformation, in 1572, Gotland was made into its own Diocese, and the church designated its cathedral.
There is not much left of the original interior. The font is made of local red marble in the 13th century. The pulpit was made in Lübeck in 1684. There are 400 graves under the church floor.