Gavi was built by incorporating a pre-existing castle built, according to legend, at the time of the Saracen occupations and anointed by Princess Gavia who had established her residence in that location. The first document that testifies to the existence of the castle is a notarial act dating back to the year 973.
The castle remained the property of the Genoese, albeit with ups and downs, at least until 1418 when it passed first to the Milanese Lordship of the Visconti, then to the Fregoso family and finally to the Alexandrian Guasco, lords of Francavilla.
Over the centuries the transformation from castle to fort has been slow but constant: the first radical interventions on the original structure were made in 1540 by the military engineer in the service of the Republic Giovanni Maria Olgiati.Disarmed in 1859, the fort was transformed into a civil penitentiary. During the First World War it was used as a prison camp for the Austro-Hungarians, while during the Second World War it was used as a prison camp for Anglo-American officers. The fortress can be visited in the various main rooms.
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.