The parish church is dedicated to Saint Aelhaiarn, but has sometimes been erroneously recorded as dedicated to Saint Giles, All Saints, and Saint Tysilio. The church is a very well-preserved 14th century church with an earlier tower, on the site of a pre-Norman church perhaps founded by the saint himself. There is an exceptional 14th century nave roof and a painted Tudor ceiling in the chancel. The tower of the present church dates to about 1300.
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.