Slangenburg Castle was constructed in the Late Medieval period. In the 17th century the castle became the property of General Frederik Johan van Baer, also known as General Slangenburg, who rebuilt it for residential purposes.
The last private owners were a German family called Passmann, who are buried in a private cemetery next to the moat. After the World War II all German properties were confiscated by the Dutch government, who thus acquired the castle, which, with the surrounding terrain and the buildings within the outer moat, now forms part of the portfolio of the Rijksgebouwendienst ('Royal Buildings Service'), while the surrounding area falls under the care of the Dutch environmental agency, the Staatsbosbeheer.
At present the castle is used as a guesthouse by the nearby Benedictine monastery, St. Willibrord's Abbey, a newly built structure of the 1950s situated on a part of the castle's former estate. The original monastic community, from Oosterhout Abbey, was initially accommodated in the castle itself in the years immediately following the war.
The estate and the monastery chapel are open to the public. The estate, roughly trapezoid in shape, features a system of lanes which is centuries old.
References: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.