Broborg is one of Uppland's most magnificent ancient strongholds, strategically placed on a ridge along the former seaway, the "highway" of its day, that led Vikings to Old Uppsala and the Baltic Sea. The castle was built on a high hill, about 40 m above sea level. The castle was used between 6th and 11th centuries.
The castle had an outer and inner wall. The outer wall protected the longest sides to the south and east.The inner wall is almost completely enclosed and has a circumference of about 200 m. There were entrances in the southeast and west.
The visible walls of the stronghold tell its history and the many sagas associated with the site capture our imagination. One such saga is about Grimsa, the daughter of a powerful Viking chieftain who lies buried in a mound near the stronghold.
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.