The Synagogue of Santa María la Blanca was erected in 1180, according to an inscription on a beam, it is disputably considered the oldest synagogue building in Europe still standing. It is now owned and preserved by the Catholic Church.
Its stylistic and cultural classification is unique among surviving buildings as it was constructed under the Christian Kingdom of Castile by Islamic architects for Jewish use. It is considered a symbol of the cooperation that existed among the three cultures that populated the Iberian Peninsula during the Middle Ages.
The synagogue is a Mudéjar construction, created by Moorish architects for non-Islamic purposes. But it can also be considered one of the finest example of Almohad architecture because of its construction elements and style. The plain white interior walls as well as the use of brick and of pillars instead of columns are characteristics of Almohad architecture. There are also nuances in its architectural classification, because although it was constructed as a synagogue, its hypostyle room and the lack of a women's gallery make it closer in character to a mosque. Though it does not have a women's gallery today, an early twentieth century architect suggested that it did at one time have a one.
The synagogue was turned into a church in 1405 or 1411, but without any major renovations. It took at that time the name of Santa María la Blanca (Saint Mary the White) and today it is most commonly known by this name.
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.