St. Andreas Castle is a privately owned castle located in Cham, in the Canton of Zug. The castle hill has been used since at least 400 AD, based on Roman artifacts found there. The site of the neighboring chapel has been used for religious ceremonies since the Roman era. During the 8th century the chapel site was used by a 'holy bishop without a name' for Christian services.
Today the castle and chapel are located on a 67,000 square metres private park. While the castle is privately owned, the grounds are opened to the public twice a year.
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.