Although Siersberg Castle was first mentioned in 1178, it was probably already built in the 11th century. It was built atop an almost 300-meter-high mountain overlooking the valleys of the rivers Saar and Nied.
During the Thirty Years' War, in 1634, the castle was taken by French troops. In the next decades it was taken and retaken several times by both parties, which of course caused damage to the castle. In 1670 the French again occupied Lorraine. When they retreated again in 1677 they partly blew up the, by then already dilapidated, castle. After that, Sierberg increasingly lost its military importance and its decay progressed.
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.