Altena Castle was erected by the brothers Adolf and Everhard von Berg around the year 1108 after Henry V granted them land in Sauerland. On Wulfseck Mountain they built their castle, which they named Wulfeshagen, later Altena. This is one of the three legends of the establishment of the county of Altena and the building of the castle.
After the acquisition of Mark near the city of Hamm in 1198, the counts of Altena took Mark Castle as their primary residence and called themselves the Counts of the Mark. They occasionally inhabited Altena Castle and from 1392 onward it was used as a residence for the county bailiff (Amtmann).
In 1912, Richard Schirrmann established the world's first youth hostel within the castle, which is still in use today (Jugendherberge Burg Altena).
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.