The Cathedral of St Andrew was built in 1158 and became the centre of the Medieval Catholic Church in Scotland as the seat of the Archdiocese of St Andrews and the Bishops and Archbishops of St Andrews. It fell into disuse and ruin after Catholic mass was outlawed during the 16th-century Scottish Reformation. It is currently a monument in the custody of Historic Environment Scotland. The ruins indicate that the building was approximately 119 m long, and is the largest church to have been built in Scotland.
The west end was blown down in a storm and rebuilt between 1272 and 1279. The cathedral was finally completed in 1318 and featured a central tower and six turrets; of these remain two at the east and one of the two at the western extremity, rising to a height of 30 metres. On the 5th of July it was consecrated in the presence of King Robert I, who, according to legend, rode up the aisle on his horse.
A fire partly destroyed the building in 1378; restoration and further embellishment were completed in 1440.
In June 1559 during the Reformation, a Protestant mob incited by the preaching of John Knox ransacked the cathedral; the interior of the building was destroyed. The cathedral fell into decline following the attack and became a source of building material for the town. By 1561 it had been abandoned and left to fall into ruin.
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.