Rosenburg castle is one of Austria's most visited Renaissance castles. It is situated in the middle of a nature reserve which adds to its appeal. The Rosenburg was mentioned in a document for the first time in 1175, in relation to the area of the border along the Kamp River between Poigreich and the Babenberg settlements with the centres, the Benedictine Altenburg Abbey and the Gars-Thunau castle complex.
The Grabner brothers acquired the Rosenburg in 1487. From 1593–97, under the rule and by order of Sebastian Grabner, a Lutheran, most of the Gothic Rosenburg was demolished and the castle was reconstructed in Renaissance style with 13 towers. The Rosenburg remained in the possession of the Grabner family until 1604.
Finally, the Rosenburg became the property of the House of Sprinzenstein. A period of neglect followed, then several tragedies struck. Lightning caused a fire in 1721, and another fire broke out in 1751 which destroyed part of the courtyard gate and the chapel. In 1800, another fire damaged the Rosenburg; it was barely used for some 60 years thereafter. Fortunately, the Romantic Era caused a renewed interest in castles, and the castle was renovated by Count Ernst Carl von Hoyos-Sprinzenstein senior rebuilt the castle at great personal expense between 1859 and 1889. The castle is now a museum.References:
Kristiansten Fortress was built to protect the city against attack from the east. Construction was finished in 1685. General Johan Caspar von Cicignon, who was chief inspector of kuks fortifications, was responsible for the new town plan of Trondheim after the great fire of 18 April 1681. He also made the plans for the construction of Kristiansten Fortress.
The fortress was built during the period from 1682 to 1684 and strengthened to a complete defence fortification in 1691 by building an advanced post Kristiandsands bastion in the east and in 1695 with the now vanished Møllenberg skanse by the river Nidelven. These fortifications were encircled by a continuous palisade and thereby connected to the fortified city. In 1750 the fortress was modernized with new bastions and casemates to protect against mortar artillery.