Rüeggisberg Priory was founded between 1072 and 1076 by Lütold of Rümligen. He granted the property and estates to Cluny Abbey making it the first Cluniac house in the German-speaking world. Under Cuno of Siegburg and Ulrich of Zell the first cells were built. Construction of the Romanesque church lasted from about 1100 to about 1185, of which there still remain the north transept and parts of the crossing tower. The Priory was dependent on Cluny Abbey and normally had a prior and two to four monks from Cluny. In 1148, it had two priories that were dependent on Rüeggisberg, in Röthenbach im Emmental and Alterswil.
At its peak the priory controlled estates throughout what is now the Canton of Bern, including Guggisberg, Alterswil, Plaffeien and Schwarzenburg as well as scattered farm houses and vineyards on the shores of Lake Biel.
The priory was one of the most important monastic houses of Switzerland during the Middle Ages, but in the late medieval period decline set in, and in 1484 it was incorporated into the newly built college of the Augustinian Canons of Bern Minster. By 1532, when much of the town was destroyed in a fire, the Priory was abandoned. The church was shut down in 1541 during the Reformation. The monastic buildings thereafter served as a source of building stone and partly as a barn.
Between 1938 and 1947 on an archaeological dig the old foundations were again laid bare, as may be seen in the little museum next to the rectory.
The ruins are generally open to the public, though they may be reserved for picnics or other gatherings. Each November an advent market is held in the ruins and over the years a variety of open air plays and concerts have been held here. Between Easter and September, church services are held monthly in the ruins.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.