The structure of the arsenal consists of two large stone-built halls with vaulting supported by repeated pointed arches. The vaulting rests on ten piers, originally there were twenty two, the missing twelve and the structure they supported having been lost to centuries of coastal erosion. The main function of the arsenal was the building, repair and storage of warships. Amalfitan war-galleys were among the largest to be found in the Mediterranean during the Early Middle Ages.
The building now contains architectural and sculptural remains, a row-barge used in the Historical Regatta, a number of models of ships and it also acts as a venue for visual art exhibitions. Starting from December 2010, the Ancient Arsenals of Amalfi host the Compass Museum on the premises of the two aisles of the building, which were spared by the Amalfi seaquake of 1343.
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.