The site of current Seeburg castle was mentioned first time in 740 AD. The construction of current castle was started in the 11th century (around 1036). It was largely extended by Wichmann von Seeburg, later Archbishop of Magdeburg (1115-1192). The next renovations took place in the 14th and 15th centuries, when the castle was flanked by towers and a gatehouse under the rule of Counts of Mansfeld.
Later Seeburg was left to decay until the Counts of Ingenheim sold it in 1880 to the Wendenburg family. In 1923, Erich Wendenburg commissioned the architect Paul Schultze-Naumburg to completely restore the building in neo-Gothic style.
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.