Hovedøya Abbey was a Cistercian founded on 18 May 1147 by monks from Kirkstead Abbey in England on Hovedøya island, and dedicated to the Blessed Virgin Mary and Saint Edmund. A church dedicated to Edmund already stood on the island, and the monks took this over as the abbey church, modifying it to meet Cistercian requirements. The rest of the monastery follow a modified Cistercian building plan, to take into account a small local hill. The church itself is built in Romanesque style; the rest of the monastery was presumably Gothic. During the medieval period the abbey was one of the richest institutions in Norway, holding over 400 properties, including a fishery and timber yards.
Political turmoil during the succession to the throne of Denmark-Norway led to the end of the monastery. The abbot, having supported the Protestant King Christian II, possibly in a bid to gain support in the face of the coming Reformation, came into conflict with the commandant of Akershus Fortress, Mogens Gyllenstierne, who ironically had supported the Roman Catholic Prince Frederick I. In 1532 the abbot was thrown into prison for his political involvements, and the abbey was looted and then set ablaze, thus ending 400 years of monastic activity at Hovedøya. Any hope the order might have had in restoring the rich abbey was dashed 4 years later, when the Reformation swept over Denmark-Norway.
The site was later used as a quarry for stone for Akershus Castle. The remaining ruins are nevertheless among the most complete of a medieval Norwegian monastery.
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.