The ruins located within the walls of Peel Castle are those of the former Cathedral of St German. Like the structures throughout the castle grounds, the cathedral's roof is completely missing. Robert Anderson examined the ruins to determine what repairs were required to restore the cathedral, and he reported to the island's Lieutenant Governor in 1877. However, none of the suggested repairs were carried out.
There is a pointed barrel-vaulted crypt below the chancel, measuring 10 × 5 × 3 metres, sloping to the entrance at the east. There is a cemetery in what was once the cathedral's nave.
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.