The chapel which opens at the beginning of the right transept of the cathedral is the most important Marian shrine in Siena; it holds the image of Most Holy Mary of Grace Advocate of the Sienese, the work of the painter Dietisalvi di Speme and better known as the Madonna del Voto (“The Madonna of the Vow”). For centuries the Sienese have turned to her in moments of trial, whether personal or communal, as the numerous ex votos hanging on the walls of the chapel bear witness, donated to the Virgin by the faithful as a sign of thanksgiving.

According to tradition, the people of Siena made a vow in front of this painting, consecrating the city to Siena on the eve of the battle of Montaperti (1260), when the Sienese defeated the superior Florentine troops, bringing the city to its highest moment of splendor. In reality, the vow was made in front of another painting, showing the Virgin and Child enthroned, known as the Madonna of the Big Eyes, one of the earliest paintings of the Sienese school, painted in the second quarter of the thirteenth century by the Master of Tressa and now kept in the Museo dell’Opera.

The Madonna of the Vow was commissioned to Dietisalvi di Speme precisely as a result of the Sienese victory at Montaperti and is usually dated around 1270. Originally placed on an altar in the right aisle of the cathedral, the image soon became the object of great . . .