Rijksmuseum on Instagram: "Jan van Goyen, who was born on this day in 1596, was one of the most prolific artists of the 17th century. Around 1,200 paintings and 800 drawings are known by him. Here, Van Goyen depicted the Valkhof in Nijmegen, one of the most important medieval sites in the Netherlands. Emperor Frederick I, a.k.a. Barbarossa, ordered it to be built on this particular spot in the 12th century, because legend had it that buildings erected by Charlemagne and Julius Caesar had…