In 1572, during the Eighty Year War with the Spaniards, Sea Beggars (Calvinist Dutch nobles) captured Brielle. After this work began on replacing the Medieval town walls with a modern fortress. This process of modernisation and replacement continued until 1713. The fortress ring has nine bastions and five ravelins and was designed by the fortress builders Willem Paen and Menno van Coehoorn. Since 1713 there have been few changes to the fortress, so the defences are some of the most important fortifications remaining in the Netherlands. It is possible to walk all the way around the walls to view them. Besides the walls there are also various buildings in the town centre which once had a military function, such as the Arsenaal, the Infirmerie and the Hoofdwacht (main guardhouse).
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.