Bilstein castle is located on a spur which falls away steeply on three sides so that the castle's defences only needed to be oriented towards the hill to the northeast. The appearance of the castle is thus dominated by its two round towers, each with a diameter of about eight metres: the Chapel Tower in the northwest and the Hohnekamp Tower in the southeast. The towers are connected by a tunnel under the castle courtyard, above ground is a 20th century archway.
The castle was built between 1202-1225. The Electorate of Cologne conquered it after a siege in 1445. Later it has been used for administrative purposes.
The northwestern wing of the main ward and the central block in the southwest are historical structures. By contrast, the wing in the southeast was built in 1978 to expand the hostel. On the valley side of the central block is a portal terrace (Söller) on which a prominent lime tree is growing.
Today a brick bridge spans the moat between the inner and outer baileys. The moat has been partly filled-in and is about 15 metres wide. The outer bailey comprises three buildings, which are referred to as the gatehouse, timber-framed house and festival hall.
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.