San Nicandro castle as we see it today dates from the 15th century although it was built on the site of a much more older fortress dating from the Norman and Swabian periods.
The castle is trapeze shaped with four corner towers, and was renovated during the 17th century. On the north side there are two square towers, one of which is one of the original towers, while on the south side there are two round towers built by the Aragonese which are behind the church.
The castle, which was actually built as a mansion, was the usual residence of the Della Marra and all the vassals of San Nicandro Garganico until the time of the Cattaneo Princes. In the 16th century the castle was integrated with the gateway to the east and the lodge was built that connected the castle with a large palace built between the door and the walls of the castle.
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.