Hannas Church was likely built during the latter part of the 12th century and possesses a well-preserved medieval character. The original church was a typical Romanesque structure with a semi-circular apse, choir, and nave. In the 15th century, the church was vaulted, and a robust stair-gable tower in the west, along with a porch in the north, were added.
The benches feature old folk paintings and are marked with farm numbers. The church's oldest item is the richly sculpted baptismal font by Sighraf. The font is as old as the church itself, adorned with biblical figures on the base and scenes from the Bible on the basin.
The altarpiece dates back to 1651. Additionally, there is a triumph crucifix from around the year 1300 in the church.
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.