The Chamber of the Sun and the Moon was used to greet guests arriving from the adjacent loggia of the Muses.
The room takes its name from the fresco in the vault showing the Chariots of the Sun and the Moon.
Here, the original decoration comprises the light blue background of the pavilion vault with white stucco lozenges enclosing figures, also in stucco. These figures are derived mainly from ancient coins and gems, of which Giulio Romano was a collector, but also from 16th century Italian masters Raphael and Michelangelo.

Gonzaga emblems and devices appear in the triangular compartments at the base of the vault and around the edges of the central panel.
In this homage to antiquity an allegory of the Sun and the Moon appears in the long panel in the centre of the vault.
Dusk is represented in a daring example of foreshortening. The chariot of Apollo bathed in the red light of the setting sun disappears from view as the chariot of Diana appears in the pale light of the moon, pulled by two horses. The white one represents day and the black one night, since the moon moves both by day and by night.

The work is traditionally held to be by Francesco Primaticcio, Giulio Romano’s best pupil, from a drawing by his master. Although there is no certain documentary evidence, the quality of the fresco would seem to confirm the theory, while the difference in style among the stuccoes suggests they were carried out by several hands: Nicolò da Milano, Giovan Battista Mantovano and Primaticcio himself.
The decoration of the room can be ascribed to the same period as the rest of this wing of the palazzo: 1527-28.
The highly innovative sotto in su perspective used for the Sun and Moon fresco aroused the curiosity of a great many painters during the 16th century and numerous drawings and prints appeared; artists such as Paolo Veronese began to reinterpret Giulio’s invention in new and original ways.
The decoration in the lower part of the room is instead later. In 1790 members of the Mantuan academy, feeling the room was too bare, decided to clear it out and decorate it with reproductions of sixteenth century stuccoes taken from other parts of the palazzo, and to add two casts of Roman sarcophagi from the Ducal Palace.

Volta/Vault La volta è suddivisa in losanghe digradanti verso il centro, ornate da figure a stucco ispirate al repertorio classico, in particolare a monete romane. Vi sono anche rilievi che riproducono particolari di opere di Michelangelo e Raffaello. Nei triangoli alla sommità della volta, tra le altre figurazioni compaiono le imprese della salamandra e dell’Olimpo. The vault is divided into lozenges that slope towards the centre. These are decorated with stucco figures drawn from a classical repertoire, in particular Roman coins. The relief work includes copies of works by Raphael and Michelangelo. The triangles at the summit of the vault contain the devices of the salamander and Olympus as well as other images.

Dettaglio/Detail Nel riquadro centrale, il carro del Sole e il carro della Luna, condotti rispettivamente da Apollo e Diana, sono dipinti con un potente effetto di scorcio. In the central panel the Sun chariot and Moon chariot, driven respectively by Apollo and Diana, are dramatically foreshortened.