The Chapel of the Vaults, also called the Chapel of the Miracles, is the starting point for getting to know the figure of Saint Catherine.
In this space, which is raised higher than the rest of the nave, where the Dominican tertiaries (called 'mantellate' because they wore a cloak, mantello in Italian) would gather to pray, Catherine lived a large part of her extraordinary mystical experience.
It is in this chapel that she, at a very young age, donned the habit of the Third Order of Saint Dominic, becoming a Mantellata after deciding to consecrate her entire existence to God. It was here, too, that the Saint, withdrawn in prayer, was struck by frequent bouts of ecstasy, during which she would lean on the octagonal pillar on the open side of the chapel. Her continuing conversations with Jesus Christ which took place here and were faithfully transcribed by her disciples were the source of the Dialogue on Divine Providence, her most important work of doctrine.
Entering the chapel and turning left, you see the painting of Saint Catherine and a Follower, by Andrea Vanni. This is a fresco that was originally on the adjoining wall, forming a corner with the church; it was detached and moved to its current location in 1667. This painting is exceptionally important because it was made when Catherine was still alive; thus it is rightly considered to be her ‘vera imago,’ a true portrait of her facial features. This is further confirmed by the fact that Andrea Vanni was a faithful disciple of the Saint, who wrote to him some of the letters that appear in her Epistolary. With this work, the artist wanted to express all his devotion to the woman he considered “mother and teacher.” In the fresco, Catherine appears in the white habit and black cloak of the 'mantellate'; she hold a lily, the symbol of purity, which over time would become her traditional iconographical attribute. Observing her hands, you will note that they bear the stigmata; this important detail enables us to establish with certainty that the painting was made after 1 April 1375, when Catherine received the stigmata in the church of Santa Cristina in Pisa. The young woman kneeling in an attitude of devotion is a disciple, a symbol of all Catherine’s spiritual children, yesterday as today, and of all those who want to know her life, works, and message of peace.
On the opposite wall are two paintings presenting the main miracles which took place right in this chapel and are reported by Catherine’s biographer and confessor, Raymond of Capua, in the Legenda Major. In one of these, the Saint gives her clothes to Jesus, who appears to her in the guise of a pilgrim. The recognition of Jesus in the poor is a common trait of the lives of many Saints and the reason for their bursts of charity. In the second picture, Jesus returns to Catherine the cross from the rosary that she herself had given to Him. Both canvases are by the Sienese painter Crescenzio Gambarelli and are dated 1602.
The remaining paintings that can be admired in the chapel retrace other moments in the Saint’s life. To the sides of the wall facing the entrance are two paintings by Crescenzio Gambarelli, both dated 1602, depicting Saint Catherine Reciting the Divine Office in Jesus’ Company and The Death of Saint Catherine. In the center is Saint Catherine Appearing to Saint Rose of Lima, the work of the Sienese artist Deifebo Burbarini.
In the center of the right wall is a major painting made by Mattia Preti between 1672 and 1673, when the artist was staying in Malta. The work, commissioned by the Piccolomini family for their altar in the Basilica of San Francesco, was moved to San Domenico in 1890 and placed in the Chapel of the Vaults. The canvas depicts the solemn historic moment when Pope Pius II, Enea Silvio Piccolomini of Siena, blesses his nephew Francesco Piccolomini, Archbishop of Siena, after handing him the papal bull of canonization of Saint Catherine, that is to say the official declaration of her sainthood, on 29 June 1461.