Corbera Castle is an impressive Muslim fortress, whose foundations lay on Roman remains. It has an irregular base, following the shape of the hill on which it rests. It was constructed in the 11th century to control the foothills of Murta and the coast. It is still possible to see the wall, the buttresses of the parade enclosure and the albarrana tower, which dates back to the Almohad period and it is one of the best-preserved towers in Europe. The complex was almost totally destroyed in 1521, during the Revolt of the Brotherhoods.
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.