Caltavuturo Castle clings to the top of the hill called Terravecchia, overlooking the modern small town to the north. It was originally the city's medieval core, completely abandoned for a different site (that of the modern town) only in modern times. The origins date from the Arab period.
Some massive parts of the walls remain, being a curtain wall of quadrangular plan and another semi-cylindrical tower to protect the access on the north side.
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.