Construction of the Tui Cathedral began in 1120, but it was not consecrated until 1225 under the reign of Alfonso IX. It looks like a fortress because of its crenellated towers. Its structure is clearly Romanesque and later diverse decorative Gothic elements were added. From the Romanesque period there are the capitals that top the interior columns, and from the Gothic period there is the portico of the main entrance.
The main chapel located in the choir was completed in 1699 by Castro Canseco. The interior has a large prominent retablo de la Expectacion, and a large altar of relics in the Chapel of the Relics.
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.