Montclair castle was built by Arnulf von Walecourt in the late 12th century. The site was a fief from Trier archbishop. The castle was built to the site of old Frankish castle. In 1351 the castle was conquered and razed by the troops of Archbishop Baldwin of Luxembourg. Jakob von Sierck built the new castle in 1434-1439. It fell into disrepair and started to decay in the 17th century. Montclair was restored in 1992-1993.
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.