The Vastseliina Castle was a castle of the Livonian Order, Bishopric of Dorpat. It was constructed in 1342 by the Landmeister Burkhard von Dreileben as part of the border fortifications of Old Livonia against Novgorod, Pskov and later Moscow. In the Middle Ages, Vastseliina Castle was well known in the Catholic world as a popular destination for pilgrims. They worshipped the holy cross in the castle chapel and a visit to the chapel gave them sanctification for 40 days – it was first validated by Pope Innocentius VI in 1354.
The castle met its end during the Great Northern War when it was demolished by Russian troops (1702). Today the ruins are open to the public.
Reference: Wikipedia, VisitEstonia
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.