Kastelburg castle was built between 1260 and 1270 by the Lords of Schwarzenberg. Like the Schwarzenburg on the opposite side of the valley its purpose was to defend the town Waldkirch and to control the trade route through the Elz valley.
The first inhabitant of the castle was Johann I of Schwarzenberg. The Schwarzenbergs died out already in 1345 and the castle was sold to Martin Malterer from Freiburg who fell in 1386 in the Battle of Sempach. In 1429 the castle was passed on to Berthold of Staufen.
In the Thirty Years' War the castle was destroyed by troops of the Kaiser on 14 March 1634 so that it did not fall into the hands of the advancing Swedish troops.
In recent years attempts have been made to conserve the edificial structure of the ruin that is standing romantically above the historic center of Waldkirch.
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.