This work deals with Malberg Castle in the Südeifel, a former medieval fortress that underwent extensive changes in the first decade of the 18th century. The castle remained privately owned until its sale in 1990 to the Kyllburg municipal association. Its remote location and the fact that it was not accessible to interested visitors until 1990 left it largely unexplored by scholars until then. The site was first scientifically examined in 1978 as part of a monograph on the architect Matteo Alberti, who worked at the Düsseldorf court and was the architect of Malberg Castle. At the same time, the same author published a small castle guide. It was only after the sale of the castle complex and the subsequent renovation work that a more detailed scientific examination became possible.