Ragnhildsholmen was a medieval castle built by Håkon Håkonsson (Haakon IV) of Norway around the year 1250. The castle was first time mentioned in 1275. In 1304 it was donated to duke Erik in 1304 and saw the power struggle between Swedish Kings Birger and Magnus III. After the near Bohus Fortress completed, Ragnhildsholmen lost its purpose. It was demolished and stones were probably used to build Bohus. Today impressive ruins still stands on the site.
References:Kakesbeck is one of the largest medieval fortifications in Münsterland and the oldest castle in Lüdinghausen. The imposingly grown complex originated in 1120 as a motte, a small hilltop tower castle. After numerous changes of ownership, the castle was extended onto two islands, but it was not until the 14th century that it underwent significant alterations and extensions under the von Oer family. The estate experienced its heyday in the middle of the 18th century, when it covered an area of almost one square kilometre and consisted of five further outer castles in addition to the core castle, which were secured by ramparts and moats.
The well-maintained condition of the castle today is thanks to the late Wilfried Grewing, the former lord of the castle. The foundation named after him has been particularly committed to preserving the property since 2020.