The Church of St John the Baptist was founded by William FitzOsbern and given to an abbey in Normandy. The nave may be 11th century, as may be the Norman font. A north aisle was added at the end of the 12th century and a south aisle shortly afterwards. In the 14th century the chancel was rebuilt and the south porch was added. In the 15th century a chapel was added south of the chancel and east of the south aisle, and a four-centred arch was inserted in the south wall of the chancel to link it with the chapel. The north aisle was demolished, its arcade filled in and two-light Perpendicular Gothic windows inserted in each of the filled-in arches. The Perpendicular Gothic west tower was added towards the end of the 15th century. The square-headed windows in the south aisle were inserted in the 16th century and the spire was added to the tower probably early in the 17th century.
On the wall can be found a memorial portrait by John Flaxman, showing a woman holding pelicans in her hand in relief. The chancel has a modern reredos.
In front of the porch is a 19th-century Celtic cross by Joseph Clarke on the four steps of the old churchyard cross.
Near the Celtic cross a marble monument marks the grave of Edward Edwards, (1812–1886) the pioneer of the public library movement. The churchyard also contains four Commonwealth war graves of service personnel, three from World War I and one from World War II.
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.