The Lower Rhine around Kleve, Emmerich and Rees was a complicated region in the 14th century. The archbishops of Cologne, the counts of Kleve and counts of Geldern eyed each other suspiciously, and jealously guarded their possessions and their rights. Between these were minor lords, all aiming to gain advantages for themselves from this situation. This mutual eyeing took place from the many castles that were scattered across the Lower Rhine landscape. They included Aspel Castle and Hueth Castle as well as Rosau Castle. They were fortifications, but they functioned more as centres of administration and jurisdiction. A bailiff took care of his master's business here, and earned a good living doing so. This tower is the remains of Rosau Castle. In later times it was used as a windmill, but the cylindrical shape is a definite reminder of its fortification days. The door halfway up is a sign of this. Doors like this were designed to make access more difficult for the enemy because it's not easy to haul a battering ram up a wobbly wooden staircase. Rosau Castle was built in the 14th century as the official seat of the counts of Kleve and for a time their bailiff administered the Hetter district from here. Today, if we look from the dyke immediately behind the tower, we can see an Old Rhine oxbow lake. So the castle was originally located right on the river. The fight against the constantly gnawing river was probably quite expensive because Duke Johann von Kleve gave up Rosau Castle as an administrative seat as early as 1482 and handed it over to his bailiff as a fief. Wars and changes of ownership did not do it any good in the subsequent centuries, with the result that there are hardly any traces of the complex today, apart from the tower.