The departure of Ludovico il Moro from Milan in August 1499, opened a period of hardship for the city and the castle, marked by conflict, occupation, brief returns of the Sforza heirs and continued foreign domination.

It was precisely the "mulberry room" painted by Leonardo, which on 25 June 1511 served as the sumptuous backdrop to the ceremony in which the French governor of Milan, François II d'Orleans Count of Dunois and Duke of Longueville handed power over to the young Gaston de Foix, Duke of Nemours, as narrated by Alberto Vignati in his historic memoirs of 1519.

Over a century later an assessment by the engineers Ricchino and Pessina describing the painted square room, informs us that Spanish alterations at least spared Leonardo’s ceiling, which was later whitewashed. There followed a period of about a hundred years in which the ground floor of the tower, as well as the adjacent rooms of the ducal apartments were used as stables.