Only foundations and one gate-tower have survived of the so-called fortified Tafelgut that used to belong to the bishop of Tallinn.
The castle was erected on a hill by the Porkuni lake in 1479 by Simon von der Borch. Cannon towers stood in the corners of the camp castle shaped as an irregular rectangle. The circular wall and the towers did not probably reach their height all at the same time, but in the course of a longer period. This claim is backed up by the gate tower - rectangular at the bottom and octagonal at the top. The machicolation frieze adorning the top of the tower dates back to a much later time, as proved by comparing the engravings of Porkuni produced in the 17th and 19th centuries. The castle was severely damaged during the Livonian War. The castle tower currently houses museums.
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.