According to tradition, the Benedictine abbey of Herrenchiemsee was established about 765 by Duke Tassilo III of Bavaria at the northern tip of the Herreninsel. New findings however indicate an even earlier foundation around 620-629 by the missionary Saint Eustace of Luxeuil.
In 969 Emperor Otto I consigned the abbey to the Archbishops of Salzburg, who in about 1130 re-established Herrenchiemsee as a monastery of Canons Regular living under the Augustinian rule. In 1215, with the approval of Pope Innocent III, Prince-Bishop Eberhard von Regensburg made the monastery church the cathedral of a diocese in its own right, the Bishopric of Chiemsee, including several parishes on the mainland and in Tyrol.
In the course of the German Mediatisation, Herrenchiemsee Abbey was secularised in 1803 and the Chiemsee bishopric finally dissolved in 1808. The island was then sold; various owners demolished the cathedral and turned the abbey into a brewery. Plans for the complete deforestation of the island were blocked by King Ludwig II, who acquired Herrenchiemsee in 1873. He had the leftover buildings converted for his private use, the complex that later became known as the 'Old Palace', where he stayed surveying the construction of the New Herrenchiemsee Palace.
References:Château de Niort is a medieval castle in the French town of Niort. It consists of two square towers, linked by a 15th-century building and dominates the Sèvre Niortaise valley.
The two donjons are the only remaining part of the castle. The castle was started by Henry II Plantagenet in the 12th century and completed by Richard the Lionheart. It was defended by a rectangular curtain wall and was damaged during the Wars of Religion. In the 18th century, the castle served as a prison.
The present keeps were the central point of a massive fortress. The southern keep is 28m tall, reinforced with turrets. The northern tower is slightly shorter at 23m. Both are flanked with circular turrets at the corners as well as semicircular buttresses. Each of the towers has a spiral staircase serving the upper floors. The Romanesque architecture is of a high quality with the dressed stones closely jointed.