Fort Nieulay, located along the Avenue Pierre Coubertin, was originally dated to the 12th or 13th century. During the English invasion in 1346, sluices gates were added as water defences and a fort was built up around it in 1525 on the principle that the people of the fort could defend the town by flooding it. In April and May 1677, Louis XIV and Vauban visited Calais and ordered a complete rebuilding of Fort Nieulay. It was completed in 1679, with the purpose to protect the bridge of Nieulay crossing the Hames River. By 1815 the fort had fallen into a ruined state and it wasn't until 1903 that it was sold and improved by its farmer tenants. The fort was briefly the site of a low-key scuffle with Germans in May 1940.
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.