St. Catherine's Church in Middelhagen, with boulder foundations, was built around 1455. The wooden tower was created only later – according to the strict rules of the Cistercian monks, many churches were built without towers. The Catherine's altar from the Middle Ages (c.1480) is still preserved – it was probably installed here only after the Thirty Years' War, having been brought from Stralsund to Middelhagen. Another very valuable piece is a chalice dating from 1597; it is made of gilded silver.
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.