At the facade of an old canal-house in Amsterdam you can find this nice memorial stone of the "Four Sons of Aymon". It is a medieval tale spun around the four sons of the Duke of Aymon, the knight Renaud de Montauban, his brothers Guichard, Allard and Richardet, their magical horse Bayard, their adventures and revolt against the emperor Charlemagne. It is a rather complicated story too long to tell here, but if you are interested you can read here.
The house is situated at a corner of the "Herengracht"and the Leidsegracht" and dates from 1672. Originally there had been a bakery of Jan Specht (Jack Woodpecker). He ordered to built that house with the four sons of Aymond in the facade. I don't know why, maybe he liked the story. In the 19th century the facade of the shop changed. It is one of the many State Monuments in the Amsterdam innercity.