Artist Combolution made a playing card with the kings Charlemagne and Frederik Barbarossa on it. For their portraits he was inspired by (almost) contemporary images. We know of Charlemagne that he was exceptionally tall for the time in which he lived; recent research states that he must have been between 1.79 and 1.92 meters tall. In contrast to historical reality, Charlemagne is often depicted with a full beard - however, this only later became a sign of royal dignity. It is much more likely that Karel wore a so-called Gallic drooping moustache. We know a little more about Frederik's appearance. His nickname "Barbarossa" ("Redbeard") refers to the ruddy color that adorned his beard.

Charlemagne had a palace built on the Valkhof Hill in 777. We don't know what this small palace looked like. It was set on fire in 882 by Vikings who had sailed up the Waal. The Viking boat next to the portrait of Charlemagne has been further elaborated under the roof. The Vikings led by Godfried de Noorman had spent the winter of 881 there. Karel's successors failed to drive the Vikings out of Nijmegen and eventually guaranteed them a safe retreat. Later, Godfried even received Frisia (area on the Dutch and Frisian coast) from the emperor. It was the only way to keep the Vikings quiet.

In 1155, Barbarossa rebuilt Charlemagne's palace and added even more. A number of still existing buildings, such as the Sint Nicolaas chapel, were incorporated into this structure. The result was the famous Valkhof castle, which can be seen in many early modern paintings of Nijmegen. The castle disappeared from the skyline of the city at the end of the 18th century. The castle, which had already fallen into disrepair, was demolished and sold as building material. The only remaining building from the time of Barbarossa is the so-called Barbarossa Ruin. The reuse of Roman columns in this structure shows that kings such as Charles and Barbarossa still aligned themselves with the Romans.