Some of the library’s rooms feature elegant frescoed ceilings: particularly noteworthy are those of the six rooms preceding the monumental hall, all characterised by plant and scroll motifs. Among these, the ceilings of three rooms stand out for their extraordinariness: the reception room, with decorations running along the entire rectangular perimeter, floral garlands, various ornamental motifs and, on the short sides, the eagle with spread wings inside an oval and the Casanate family coat of arms (a tower surmounted by a star with eight rays).
Then the two rooms preceding the Monumental Hall. The first has garlands and polychrome floral decorations on a white base, with two decorative elements in the centre: surmounted by other symbolic elements, a dog with a torch in its jaws, an emblem of fidelity to the Gospel message and its dissemination by the Preaching Friars; and the Casanate coat of arms surmounted by the wide-brimmed hat.
On the ceiling of the next room, containing the library’s historical archives, is the 1736 fresco by Giovanni Mazzetti where, amidst numerous polychrome and floral decorations, the Glory of St. Thomas is depicted: the saint in a dominican habit is accompanied to heaven by his master St. Albert the Great who, wearing golden robes, is kneeling in adoration of the divine trinity, surrounded by putti holding his tiara, pastoral baculum, and the open book symbolising the word of God..
Some offices are also characterised by purely ornamental frescoed ceilings with filler motifs, plant decorations, masks, winged animals in soft colours (light green, brownish) and gilded elements.
The cycle of frescoes continues along the walls of one of the reading rooms with the nine allegorical figures representing Astronomy, Arithmetic, Dialectic, Law, Geometry, Grammar, Music, Rhetoric and Theology. Created by the painter Giuseppe Cellini in the early 20th century, they are all rendered as young women seated or standing in architecturally structured niches surrounded by whorls and festoons: an explicit reference to the illuminated decorations of the numerous manuscripts and incunabula in the library.