Burgruine Hohenburg auf Rosenberg is a ruined medieval castle probably erected in the late 11th century. The castle was first mentioned as castrum Hohenburc in an 1142 deed. It was then the seat of a Bavarian noble family, who as Counts of Lurn administered the Lurngau region within the Duchy of Carinthia. The last count, Altmann, had become Prince-Bishop of Trent in 1124, and upon his death in 1149, the castle was bequested to the Archbishopric of Salzburg and became the seat of episcopal ministeriales.
Under the mediation of Duke Ulrich III of Carinthia, in 1263 a division of the property was arranged between the Salzburg archbishops and the neighbouring Counts of Ortenburg, heirs of the extinct Counts of Lurn, who had aspired the Hohenburg estates for decades. In 1311 Archbishop Conrad IV of Salzburg enfeoffed a part of Hohenburg Castle to the sons of late Count Frederick I of Ortenburg (1247–1304). Nevertheless the residence became less important when it was replaced by nearby Feldsberg Castle as administrative seat of the Salzburg possessions. When the Ortenburg dynasty became extinct in 1418, their possessions passed to the Counts of Celje.
Today only ruins remain. The castle was probably destroyed in the 15th century conflicts between the Counts of Görz and the Habsburg emperor Frederick III over the heritage of Count Ulrich II of Celje. The former chapel was rebuilt as the Baroque St Mary's pilgrimage church (Maria in Hohenburg) in 1707.
References:Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.