The beginnings of the Wasserschloss "Haus Assen" date back to the 14th century. Under the von Ketteler family the buildings were extended to the south ("Neu-Assen"). In 1564 Goswin von Ketteler had the present Renaissance castle built by the master builder Laurenz von Brachum. In the middle of the 17th century the von Galen family acquired the manor of Assen. Under Matthias v. Galen, the neo-Gothic chapel was built in 1854-58 by Friedrich Wilhelm Buchholz and consecrated by the count's brother-in-law, the famous "social bishop" Wilhelm Emmanuel von Ketteler. Blessed Cardinal Clemens-August von Galen (1878-1946) - known as the "Lion of Münster" - often stayed at Haus Assen in his youth. His nephew, Bernhard Count von Galen, gave the castle to the Roman Catholic religious community of the Servants of Jesus and Mary (SJM) in 1997 as a gift for youth work.
Public tours are offered monthly, the dates can be found here.