16th-century decoration

The interior decoration reflects the two phases of construction: in particular, the two vestibules on the ground and main floors, completely covered in late Renaissance decoration, have survived intact. Here the inspiration to Roman models and in particular Raphaelesque ones is evident on the part of Castello, author of the design and the frescoes enclosed between the stuccoes and grottesche. On the ground floor, delicately modulated white stucco frames run between fanciful, minute grotesque decorations and larger frescoes depicting full-length Olympian deities, while the central octagons depict Juno and Leda. On the side walls and on the Vault of the vestibule of the main floor, which is brighter, the colours of the decorations become brighter. They too are entirely covered, thanks to Bergamasco's intervention, with stuccos and grotesques and frescoed panels representing Apollo Citaredo with the Muses and Musician figures. Here too the unity of the architectural and decorative project is evident.^[3]

18th-century rooms

Two rooms in particular belong to the eighteenth century phase, the chapel and the gilded gallery, masterpieces of the late Genoese Baroque due to Lorenzo De Ferrari, whose last works were completed shortly before his death in 1744. In both rooms, the decoration becomes all-embracing, blending walls, ceilings, doors, mirrors and furnishings into a sophisticated scenographic apparatus intended to amaze the spectator.

The chapel is a small enclosed room, intended to highlight the famous statue of the Virgin and Child (known as the Madonna Carrega), sculpted by Pierre Puget around 1680,^[4] which is currently on display at the Museo di Sant'Agostino and was replaced by a copy in 2004. The artist uses a fake trompe-l'œil architecture in gilded stucco and fresco to fake a colonnade open onto the garden, as a theatrical backdrop for the marble group of the Virgin, which stands out thanks to the contrast between the whiteness of the marble and the bright colours of the background. Similarly on the ceiling, the fake stucco architecture creates an oculus framing the fresco with a flight of angels. The door wings are painted on canvas by the same painter who depicted two medallions with the Annunciation and the Nativity in monochrome.

The complex decorative machine of the Galleria Dorata realised by De Ferrari probably in collaboration with Diego Francesco Carlone, represents one of the highest achievements of the late Genoese Baroque.^[5] It is placed at the end of the 18th-century structure of the palazzo, and is a significant example of the Rococo taste in Genoa. It was entirely designed by De Ferrari between 1734 and 1744 following a unitary design that blends together gilded stuccoes, mirrors and frescoes. The entire decorative cycle is inspired by the stories of Aeneas; in the central medallion of the vault and in the roundels on canvas the most important episodes in the Aeneid are depicted. On the oval of the vault is the Council of the Gods, with Venus, Aeneas' mother in the presence of Jupiter. In the two large lunettes are The Landing of Aeneas and Aeneas and Venus, while in the four roundels are The Flight from Troy, Aeneas and Dido, Venus commissioning Vulcan with Aeneas' weapons and The Defeat of Turn.