St. John's Church (Sint-Janskerk), named after St.John the Baptist, was originally built as a baptistery for the St. Servatius Chapter of Maastricht. In 1633, after a period in which it functioned as an autonomous parish church, it came into the possession of the Dutch Reformed Church, established in 1632. This as a result of the capture of Maastricht from the Spanish army in 1632 by the troops of the Seven United Provinces of the Netherlands under the command of Prince Frederik Hendrik of Orange. After the establishment of a state-church, i.e. the Dutch Reformed Church, all catholic churches had become protestant in the regions already conquered.
The Prince Bishop of Liège, the Duke of Brabant and Prince Frederik Hendrik agreed that in Maastricht in principle only smaller chapels should be handed over to the protestants. The bigger churches remained catholic, which was exceptional from a national point of view. However, already in 1633 the protestant chapels proved to be too small and after new discussions two churches, one of which was St.John's, came into the possession of the protestants. The first service of the Dutch Reformed Church took place on the 1st of January, 1634.
Since 1987 the church has been in the use of the 'Protestantse Gemeente St. Jan', a federation of two different reformed communities.
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.