San Nicolás de la Villa is one of the twelve Fernandine churches built in the city after its conquest by King Ferdinand III of Castile (1236), in Gothic-Mudéjar style, although it was completed only in the following centuries, with much renovation added in the meantime. The main portal, in Renaissance style, was added by Hernán Ruiz the Younger in the 16th century. The octagonal tower, with a defensive appearance, was rebuilt during the age of the Catholic Monarchs above an older Islamic minaret.
In the 17th and 18th century, much of the church's elements were modified until it received the current mostly Baroque appearance. The baptistery dates from 1555.
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.