The Tour du Guet is a 13th-century watchtower. It is 39 metres high and features a dovecote for carrier pigeons. The tower dates from 1214, when Philip I, Count of Boulogne built fortifications in the town. Damaged by a 1580 earthquake, it was used as alighthouse until 1848, when it became a watch tower. During World War I, it served as a military post.
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.