Isenburg Castle was built by the Counts of Isenburg around 1100 if not prior. Occupied by several branches of the Isenburg family, it was inhabited into the early 17th century. Shortly after being abandoned, it became a ruin. After the branch of Lower Isenburg had extinguished in 1664 with count Ernst of Isenburg-Grenzau, the county was partitioned between the counts of Walderdorff and the counts of Wied-Neuwied. The present owner of the castle is Maximilian, 9th Prince of Wied, son of Carl, 8th Prince of Wied and Princess Isabelle of Isenburg.
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.