Hachen Castle was built around 1000 and was first owned by Count Ezzo. In 1060, Otto von Northeim received the castle from his wife Countess Richenza, from the Ezzo family. Twenty years later, Otto's son Count Kuno von Beichlingen gave the castle to the Archbishop of Cologne in 1080. The latter granted the castle as a fief to the Counts of Dassel. In 1232, the Counts of Dassel sold the castle to the Counts of Arnsberg. When the Grafschaft was sold in 1368, the property once again fell to the Archbishopric of Cologne.
Around 1371, Hachen Castle was the widow's seat of the last Countess of Arnsberg, Anna. However, she later gave preference to Wildshausen Castle near Arnsberg. The importance of the castle declined from the 15th century onwards. The castle came into the possession of the lords von Wrede, Ketteler, von Thülen, von Ledebur and von Fürstenberg. It was not until 1839 that the castle became the property of the municipality of Hachen. The war memorial next to the castle ruins was dedicated on August 3, 1924.
The building history of the castle has not yet been sufficiently researched. Some drawings from the 18th and 19th centuries still show it as a towering ruin. Only a few documents about construction work - for example from the 15th century - have been preserved.
An investigation into the history of the building was first carried out in 1923 and then between 1978 and 1980 by the Westfalen Office for the Preservation of Monuments. A main castle area measuring 40 x 60 m was uncovered. Below the main castle there was an outer bailey on a plateau. The endangered north side was protected by a 2 m thick shield wall. Behind it was a round tower (possibly the keep) with a diameter of 8 meters. The tower was later replaced by a trapezoidal building with thick walls. Several other buildings were added.
It is still worth climbing up to the castle ruins today, as the view from there over Hachen is really beautiful.
