Sala delle Asse, south-west wall during restoration work (2016, ongoing)

In a letter dated 21st April 1498, the secretary Gualtiero da Bascapè informed the duke Ludovico maria Sforza called il Moro that Leonardo da Vinci had promised to complete by the following September the decoration of the Sala delle Asse, a large room in the north-east corner of the Castle, at the bottom of the Falconiere tower. Leonardo’s decorative design, on which collaborators may have assisted, was for a great pergola of mulberries, starting from large trees painted along the walls that grew upwards to the vault in a close tangle of branches and golden cords, woven in complicated knots of great elegance. On the vault are cartouches bearing inscriptions that record, in chronological order, the marriage (1493-94) of Ludovico il Moro’s niece, Bianca Maria Sforza, to the Emperor Maximilian, the investiture of Ludovico as duke (1495) and, lastly, his journey (1496) with Beatrice to request help from Maximilian in the war against Charles VIII. The fourth cartouche, now illegible, recorded the victory of Louis XII, king of France, over Ludovico il Moro. In the centre is a shield quartered with the arms of the Sforza and Este families.
On the room’s northern walls is a large area of preparatory drawing known as the Monochrome, depicting the powerful roots of a mulberry tree working their way into the ground and, with overwhelming strength, breaking up the square-shaped rocks and boulders. This illusionistic composition framed the mouth of the great fireplace that existed in the room in Ludovico il Moro’s day. When the French arrived and the dukedom of Milan was conquered in 1499, Leonardo had to flee the city, probably leaving this work unfinished.
The surprising choice of the mulberry tree, in Italian moro or, in Lombard dialect morone, to decorate Ludovico’s reception hall was a clear reference to his nickname of il Moro, and recalled his role in encouraging the plantation of mulberries, on which Lombardy’s flourishing silk production was based. Also, from a symbolical viewpoint, this tree, defined as sapientissima omnium arborum, was used to celebrate Ludovico’s wise policies and the stability of the dukedom under his governance.
A letter dated 1498 specified that “On Monday they will clear the big room of planks, that is, the tower room” – that is to say, the wooden planks, often used at the time to insulate rooms against cold and damp, would be removed. Based on this element, architect Luca Beltrami, who supervised the complete restoration of Sforza Castle at the end of the nineteenth century and the discovery of Leonard’s decoration, rechristened it the "Sala delle Asse (Room of Planks)". In actual fact, in Ludovico’s time the room was known as la camera detta de’moroni (the mulberry room), as recorded in chapter 20 of Luca Pacioli’s Divina Proporzione (1509).
For some time, the room’s decoration had been in a very poor state that not only threatened conservation of the artwork, but also made it difficult to decipher. From 2011, therefore, the 1950s exhibition layout of wooden planks was removed from the walls and an important programme began to investigate and analyse the artwork with a view to better understanding and restoring it, in collaboration with the Opificio delle Pietre Dure (a restoration institute in Florence) and the Ministry of Cultural Heritage. These analyses led to the discovery of a portion of ancient plaster concealed under numerous layers of limewash and repainting that ran right around all four walls in the room. The complex removal of these tenacious layers of limewash, selectively carried out using laser technique, brought to light the exceptional preparatory drawing of mighty mulberry trunks, with astoundingly naturalistic elements emerging from the trees.