The site of current Seeburg castle was mentioned first time in 740 AD. The construction of current castle was started in the 11th century (around 1036). It was largely extended by Wichmann von Seeburg, later Archbishop of Magdeburg (1115-1192). The next renovations took place in the 14th and 15th centuries, when the castle was flanked by towers and a gatehouse under the rule of Counts of Mansfeld.
Later Seeburg was left to decay until the Counts of Ingenheim sold it in 1880 to the Wendenburg family. In 1923, Erich Wendenburg commissioned the architect Paul Schultze-Naumburg to completely restore the building in neo-Gothic style.
Duino Castle was built by the Wallsee family in 1389 on the cliffs overlooking the Gulf of Trieste. It replaced an older castle from the 11th century. Over time, the Wallsee family disappeared and the castle, after having been used as a prison, became the residence of the Luogar and Hofer.
At the end of the 19th century it became the property of Prince Alexander von Thurn und Taxis from the Czech branch of the House of Thurn and Taxis. It remains with the family to this day with his great-grandson Prince Carlo Alessandro della Torre e Tasso, Duke of Castel Duino the current owner. The castle has been opened to the public as a museum and park.