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:The stone church of Gamla Uppsala, built over the pagan temple, dates from the early 12th century. Due to fire and renovations, the present church is only a remnant of the original cathedral.
Before the arrival of Christianity in Sweden, Gamla Uppsala was the seat of Swedish kings and a ceremonial site known all over northern Europe. The settlement was home to royal palaces, a royal burial ground, and a great pagan temple. The Uppsala temple, which was described in detail by Adam of Bremen in the 1070s, housed wooden statues of the Norse gods Odin, Thor and Freyr. A golden chain hung across its gables and the inside was richly decorated with gold. The temple had priests, who sacrificed to the gods according to the needs of the people.
The first Christian cathedral was probably built in the 11th century, but finished in the 12th century. The stone building may have been preceded by a wooden church and probably by the large pagan temple.