The overall view of the frescoes on the ceiling, perfectly integrated into the elegant stucco decorations by Terzani, represents the synthesis of the decorative process of the Cathedral.

The vaults are oval, with a false dome, decorated with paintings in both the central oval and the four corner segments, featuring figures of Prophets, created by Giacinto Diano in 1789. In the three central ovals, the artist depicted scenes of David showing his son Solomon the designs of the Temple of Jerusalem, Esther and Ahasuerus, and the Consecration of Solomon’s Temple.

The large dome was decorated with scenes of the Assumption and Coronation of Mary as Queen of Heaven, with hosts of angels, cherubim, saints, and prophets. Already damaged in the 1800s due to rainwater infiltration, it was demolished and later rebuilt. However, parts of the original decorative project remain, including two fragments with the heads of David and God the Father, along with Giacinto Diano’s preparatory drawing, and the pendentives depicting the four Evangelists (Saint Mark, Saint John, Saint Matthew, and Saint Luke), created in 1788.

Along with the complex fresco decoration, Giacinto Diano was commissioned to execute the twenty oil-on-canvas lunettes to be placed next to the windows. These were created between 1790 and 1791 and depict prophets (Haggai, Habakkuk, Isaiah, Daniel, Jeremiah, Ezekiel, Micah, Obadiah), Doctors of the Church (Saint Jerome, Saint Augustine, Saint Gregory the Great, Saint Ambrose), virtues (Hope, Humility, Prudence, Fortitude, Purity, Faith), and biblical heroines (Jael with Sisera and Judith with the head of Holofernes).

Paintings on canvas on the sides of the windows, created by Giacinto Diano between 1790 and 1791.

The pendentives in the dome depicting the four Evangelists, painted by Giacinto Diano in 1788