Illingen Castle was documented first time in 1359 when it was owned by Dietrich V. von Kerpen (this is why castle is also called Kerpen Castle). In the16th century it was moved to the hands of Nassau-Saarbrücken counts, who owned Illigen until French Revolution. Illingen castle was badly damaged in the Thirty Years' War and rebuilt later.
The castle started to decay after 1825 and was used as a quarry. The tower was restored in 1951 and today there is a restaurant.
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.