Kastelburg castle was built between 1260 and 1270 by the Lords of Schwarzenberg. Like the Schwarzenburg on the opposite side of the valley its purpose was to defend the town Waldkirch and to control the trade route through the Elz valley.
The first inhabitant of the castle was Johann I of Schwarzenberg. The Schwarzenbergs died out already in 1345 and the castle was sold to Martin Malterer from Freiburg who fell in 1386 in the Battle of Sempach. In 1429 the castle was passed on to Berthold of Staufen.
In the Thirty Years' War the castle was destroyed by troops of the Kaiser on 14 March 1634 so that it did not fall into the hands of the advancing Swedish troops.
In recent years attempts have been made to conserve the edificial structure of the ruin that is standing romantically above the historic center of Waldkirch.
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.