The Castle Church of Schleiden, a late-gothic three-nave hall-church with an interesting net-and-star vault, was built between 1516 and 1525 according to the plans of Johann Vianden. This Castle Church is the Catholic parish church today. On the end walls of the side aisles are precious glass paintings from 1535, a valuable König organ (constructed around 1770) and a sarcophagus made of black marble. Equally remarkable are the late-gothic glass windows, the vault paintings and the Flemish altar wing.
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.