Hardegg Castle was first mentioned in an 1145 deed, it was acquired by the Counts of Plain about 1187. Hardegg itself is first documented as a town in 1290. Located on the border with the Kingdom of Bohemia, the area was devastated during the Hussite Wars in 1425. In 1483 Hardegg was bequeathed to the Habsburg archdukes of Austria.
Emperor Maximilian I granted Hardegg to his ministeriales of the Prueschenk noble family and elevated them to immediate Counts of Hardegg in 1499. Two years later Count Ulrich purchased the Bohemian County of Kladsko from the Dukes of Münsterberg. From the Thirty Years' War onwards the castle decayed, until it was acquired by the Khevenhüller dynasty and rebuilt in the late 19th century according to plans designed by Carl Gangolf Kayser.
After World War II until the fall of the Iron Curtain, Hardegg was particularly isolated. The only connection to the Czech Republic is via a bridge built in 1874 across the Thaya to the neighbouring village of Čížov.
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.