The chapel created in 1291 by Cistercian monks assumed its present shape in 1440 when it was rebuilt as a St. Mary's brick church. The half-timber framed nave (oak beams with brick fillings) was constructed in the 16th and 17th centuries with the choir annex added in the 18th century. Later restoration works served to expose paintings from around 1470 on the walls and the triumphal arch. The oldest decorative features are the Gothic triumphal crucifix (around 1500) and the Gothic carved altar created in 1520 at Antwerp. This altar is considered one of the truly outstanding sacred works of art anywhere in Northern Germany and bears close stylistic resemblances to the Bordesholm Altar at Schleswig by Hans Brüggemann and Jan Bormann’s altar for the Güstrow parish church made in Brussels at roughly the same period. The altar was originally acquired by wealthy merchants from Stralsund for a local Church and found its way to its present location only in 1708. The pulpit was originally made for another church, too, probably again in Stralsund, and the and brass chandelier also comes from there.
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.