Tramontano Castle, begun in the early 16th century by Gian Carlo Tramontano, Count of Matera, is probably the only other structure that is above ground of any great significance outside the sassi. However, the construction remained unfinished after his assassination in the popular riot of 29 December 1514.
It has three large towers, while twelve were probably included in the original design. During some restoration work in the main square of the town, workers came across what were believed to be the main footings of another castle tower. However, on further excavation large Roman cisterns were unearthed. Whole house structures were discovered where one can see how the people of that era lived.
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.