During the 6th century AD a small community of monks settled on the Inishkeel island. Their religious leader was Saint Conall Cael, from whom the island later derived its name. During the following centuries Inishkeel was a traditional destination of pilgrimages. Remains of the church and the connected buildings as well as some carved stones can be seen on the island. For its artistical and archeological importance the island was declared National Monument. A bell known as St Conall Cael's Bell remained on Inishkeel up to the 19th century and was then acquired by the British Museum.
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.