Wilhelmstein Castle lies in the village of Bardenberg, part of the municipality of Würselen, north of the city of Aachen in the North Rhine-Westphalia region in Germany.
The first castle at this site was named Valentia Castle. It was built by the Archbishop of Cologne as a bulwark against the Duchy of Limburg. After a short time, this castle was destroyed by the troops of Limburg, in 1255.
On the remains of this earlier fortification, Wilhelmstein Castle was built in 1270 by Count Wilhelm IV of Jülich. Hence the name Wilhelmstein. From here he exercised his guardianship over the city of Aachen, which he had already gotten from the German Emperor Friedrich II in 1240. Later when Wilhelm died the castle lost its importance and was kept up by caretakers.
During the Jülich Feuds between 1538-43 the castle was considerably damaged. In 1642 the castle was taken by the troops of Weimar-Hessen during the 30-Years War. In 1690 the castle was again taken, this time by French troops. A year later they burned the castle and village to the ground because the contribution could not be paid for the support of the French occupiers. This left the castle in ruins. In 1793 the castle became state property and in 1820 it became privately owned.
The castle was built on a ledge at the eastern bank of the Worm stream, on the boundary between the Jülichgau and the Maasgau. Originally the front of the castle was protected by a ditch. Traces of the chains of the former drawbridge can still be seen. The round tower next to the Gothic gate once served as a prison. The castle had a, five storeys high, square keep, which at present only partially remains.
Today the castle harbors an open-air theater and a restaurant and is surrounded by a small forest. The castle can only be visited as a guest of the theater or restaurant.