The church of St. Olaf was built in the 1200s, but it was enlarged in 1400s. The major restoration was made in 1870s by Helgo Zettervall. The church and the locality is named after the Norwegian Saint Olaf due there is a so-called St. Olaf's Well near the church. It was a famous pilgrimage site in past centuries.
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.