The last painting on the left wall, started by the Sienese painter Alessandro Casolani and completed by his son Ilario in the second half of the sixteenth century, portrays the announcement of the birth of Jesus to the Virgin Mary. Mary, pictured on the left, is surprised by the visit of the Archangel Gabriel who greets her by handing her a white lily, the symbol of purity. With his right hand, the Archangel points to the Dove of the Holy Spirit materialising among the clouds. On the floor, in the foreground, there is a basket with a sewing set, while next to the young woman there is a table with an open book and an hourglass. This indicates that God's plan is not accomplished in an abstract dimension, but in the passing of time. An extraordinary event takes place in an everyday context: Mary agrees to accept God’s will and to become the Mother of Jesus. The girl, however, does not hide her concern and surprise to be chosen by the Lord, and by bringing her right hand to her chest she seems to be saying: “Are you sure it’s me?”
The painting’s background bears a sort of window where, previously, another painting was positioned.