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 Gravensteen is a castle in Ghent originating from the Middle Ages. The name means 'castle of the counts' in Dutch. Arnulf I (918–965), Count of Flanders, was the first to fortify this place, building a medieval bastion on this high sand dune, naturally protected by the river Leie and its marshy banks. This bastion consisted of a central wooden building and several surrounding buildings, also in wood.
In the early 11th century, the wooden building was replaced by a stone residence, consisting of three large halls that made up three storeys, connected by a stone stairwell. The monumental stone staircase, the light openings, the fireplaces built into the walls and the latrines were signs of considerable luxury and comfort in those days. There was probably also a tower.