St Mary's Church dates from the twelfth century. At this church the Rev. Legh Richmond is thought to have originated the now globally popular idea of using boards with movable numbers to indicate hymn numbers during church services. The 13th-century tower is of a very unusual style in that it is built on four piers at the entrance to the church. This is one of only four in examples in Britain. The tower contains a ring of 8 bells which the heaviest weighs 10.5cwt in the key of G. The oldest bell was made in 1594.
The current church building has aspects dating from the late 12th century onward, with the majority of the present building resulting from the alterations of the 14th and 15th centuries. The Oglander Chapel on the eastern end of the south aisle is the resting place of members of that family and includes two elaborately carved and painted wooden effigies of knights placed upon two of the tombs. Whilst installed by the family itself, their appearance does not represent the accurate historical dress of the time for the family members in the tombs beneath. In the north aisle there are funerary hatchments of the Oglander family on the walls, and two fonts from the 13th and 15th centuries.
The churchyard contains the Commonwealth war graves of four British Army soldiers of World War I.
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.