Hohenbaden Castle, built in 1102, and known locally as the Altes Schloss (Old Castle) was home from the 11th-15th century to the margraves of Baden. During its heyday in the 15th century, the castle had 100 rooms. In 1479 margraves moved their seat to Baden and the old castle started to decay. In 1599 it was destroyed by fire.
From the tower you have a good view over Baden-Baden and distant view of the Rhine valley. The courtyard of the ruins is also worth of seeing.
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.