In 1264, castrum Hackenberg is mentioned as a site for document sealing. After the last Hackenberger died, the property passed to Alber Stuchs von Trautmannsdorf in 1382. Christoph Kuenritz bought and converted it into a Renaissance castle in 1543. Plundered in 1620 during the Thirty Years' War, it remained devastated until Sigmund Friedrich von Sinzendorf purchased it in 1650. His nephew, Theodor Reichsgraf von Sinzendorf, remodeled it into a Baroque palace between 1679 and 1677. After Prosper von Sinzendorf's death in 1822, it passed to the Reuß-Köstritz princes but fell into disrepair.
In 1945, it came under Soviet administration as German property, and in 1955, it was returned to Prince Reuß. Artists from the Vienna Group, including Friedensreich Hundertwasser, moved in from 1959. Captain Josef Steiger bought it in 1974, and in 1986, Horst Wächter, Hundertwasser's former assistant, acquired it. The Osmann family took over in 2020, with Horst Wächter remaining for historical research.
The four-story structure features Renaissance geometry and proportions, with medieval foundations. A cosmological mysticism, likely embedded during the 1679 Baroque renovation, is present. The four wings align precisely with the cardinal directions, enclosing a rectangular courtyard. The southern wings retain colorful ceiling frescoes and stucco decorations.
Access is via a short alley in the northeast, crossing a stone bridge into a frescoed entrance hall, leading through the courtyard with an octagonal fountain to a three-bay shell grotto, the 'sala terrena,' decorated with statues, frescoes, shells, and stucco, extending into the garden. The former access extended over the moat to a landscaped area with a Baroque-era artificial lake.
The Initiative Hagenberg association hosts cultural events at the castle.
Rosenborg Palace was built in the period 1606-34 as Christian IV’s summerhouse just outside the ramparts of Copenhagen. Christian IV was very fond of the palace and often stayed at the castle when he resided in Copenhagen, and it was here that he died in 1648. After his death, the palace passed to his son King Frederik III, who together with his queen, Sophie Amalie, carried out several types of modernisation.
The last king who used the place as a residence was Frederik IV, and around 1720, Rosenborg was abandoned in favor of Frederiksborg Palace.Through the 1700s, considerable art treasures were collected at Rosenborg Castle, among other things items from the estates of deceased royalty and from Christiansborg after the fire there in 1794.
Soon the idea of a museum arose, and that was realised in 1833, which is The Royal Danish Collection’s official year of establishment.