Eleven fortress keys

When a castle was conquered in the Middle Ages, authority over the fortress was given to the new master by handing out the gate key. This resulted in the ceremonial handover of the keys of besieged fortresses to the victors in modern times - which was performed until the 19th century. Successful conquerors kept their fortress keys permanently. The Prussian army gained numerous fortresses and their keys entered the arsenal. To this day, it is customary in Rhenish carnival to put the city keys temporarily in the hands of the 'Narren' (fools).