The exact building time of Diemerstein Castle is unknown but the first lord Rudegar von Dimarstein was mentioned in 1216. After several owners it was destroyed in the Thirty Years' War and not rebuilt. The private residence was built to the top of castle ruins in the mid-19th century. The lower castle can be visited, but upper is in private ownership.
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.