In the year 1728, Count Franck Caspar Wilhelm von Hillesheim had built what was once called the 'farmhouse' of Arendhal. The architect Johann Adam Breunig designed not only the courtyard and the castle park but also the U-shaped farmhouse open to the castle.
Following the death of Franz Caspar Wilhelm, the construction of the castle remained unfinished. In 1785, Wilhelm Ernst Gottfried von Hillesheim, his son and an imperial count, passed away without heirs. One of his sisters then inherited the castle. She had been married since 1756 to the imperial count Ambrosius Franz von Spee (von Spee family), residing at the nearby Heltorf Castle in Angermund. She thus passed on the possession of the castle to the von Spee lineage. Since 1804, Ahrenthal Castle has been in the possession of the imperial counts von Spee. Count Wilhelm von Spee had the building constructed according to the plans of two architects from Düsseldorf, Bernard Tüschaus and Leo von Abbema.
The wood used for the construction of the castle mainly came from Vehnerwald, where traces of excavation can still be found today. In the 1920s, a fire destroyed the entire farmhouse. At that time, the reconstruction focused on the interior of the buildings at the expense of the exterior. The reconstruction and renovation did not take into account the original form of the roofs. Until today, Ahrenthal Castle has remained an agricultural organization, although since the 1990s, the estate has been expanded and developed for commercial purposes. Since 2011, it has been used for seminars.
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.