In the year 1115, fortifications were erected at the site by Gosewijn I, Lord of Valkenburg. This original wooden keep survived until 1122 when it was destroyed under siege by Henry V, Holy Roman Emperor. The castle was rebuilt in the following centuries but was again destroyed in a siege, this time by Jan III, Duke of Brabant. The current ruins are those of the castle rebuilt in the 14th century.
The castle was blown up during the Franco-Dutch War, in 1672, by the army of King-Stadtholder Willem III to prevent it falling into French hands.
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.