The Valkhof is on a hill overlooking the river. It is the site of a former Charlemagne fortification and the surviving Carolingian elements are quite modest. There are two buildings with a Carolingian element. The first is an octogon chapel built in the style of Aachen in the 8th or 9th century. The initial building was constructed about 1000 and rebuilt about 1400. It used material from Charlemagne's fortification and we think we could identify some of these Caroilingian flat bricks. The second building is the ruin of Barbarossa's chapel that incorporated several Carolingian capitals on Roman pilars in the chapel.
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.