Iburg is a ruined hill castle in Westphalia. It was build around the 8th century, dating back to the time of Charlemagne and his war with the Saxons. Today it is a popular day-trip destination and the tower, named after Charlemagne (Kaiser Karl Turm), can be climbed for beautiful views.
It is likely that the castle was originally erected by Saxons as a fortified stronghold but once conquered Charlemagne build a chapel within its confines to honour St.Peter, which he eventually gifted to the Arch-Diocese of Paderborn. From 1134 a monastery briefly used the castle before the Bishop of Paderborn fortified it to become a stronger military fortress in the late 12th century. The Iburg never saw much action, however, and slipped from importance until the 15th century, when Otto of Braunschweig destroyed it. The castle was not restored and the close-by city of Bad Driburg inherited the holdings.
First archeological surveys were undertaken on 1900 and gradually the ruins where freed and restored to serve as tourist attraction.
References: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.