The Ducey domain came into the hands of the old Norman Montgommery family in 1521 after the wedding of James Montgommery to Claude de la Boissière, the heiress to the lands of Ducey. The castle was built at the beginning of the 17th century by Gabriel II de Montgommery, one of the sons of Montgommery first who became famous for killing Henry II, king of France, by accident in a tournament on 30th June 1559. He converted to Protestantism and became one of the greatest Protestant Chiefs in the area. Gabriel caused the hatred of Catherine de Medicis and was beheaded on the Place des Grèves on 26 th June 1574. Gabriel II de Montgommery was born in 1565 an inherited the lands of Ducey. Following his father's example, he became the chief of the Protestants in the Avranches area.
Today Château des Montgommery is open to the public.
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.