Ragnhildsholmen was a medieval castle built by Håkon Håkonsson (Haakon IV) of Norway around the year 1250. The castle was first time mentioned in 1275. In 1304 it was donated to duke Erik in 1304 and saw the power struggle between Swedish Kings Birger and Magnus III. After the near Bohus Fortress completed, Ragnhildsholmen lost its purpose. It was demolished and stones were probably used to build Bohus. Today impressive ruins still stands on the site.
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.