Wartenstein castle was built around 1206 by Konrad von Zwiefalten. The castle is mentioned for the first time in 1208 and later owned for several families. In 1341 it was rebuilt and repaired by abbot Hermann II of Arbon. After the middle of the 16th century sources describe the castle dilapidated. The Abbey Pfäfers gave in 1586 the worthless site to the local residents as a quarry.
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.