Monastery of San Juan de Duero, built in the Romanesque style, consists of a single nave with a wooden roof, semicircular apse, and a pointed barrel vault. From the 12th century it belonged to the Knights Hospitaller of Jerusalem, until it was abandoned in the 18th century. The 12th century church and the 13th cloister, with Gothic and Mudéjar elements, are still standing.The arcades combine the various architectural styles current in Spain at the time: late Romanesque, early Gothic, and especially, Islamic tracery. These arches are criss-crossed to achieve a beautiful visual effect. Inside the church there is a display of items from Jewish, Islamic and Christian cultures.
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.