The central panel of the Loggia’s vault is dedicated to the myth of Phaeton, the son of Apollo, who takes his father’s chariot but, incapable of driving it, launches himself into a frenetic and dangerous ride into the sky to the point of causing Jupiter to intervene who punishes the youth’s foolhardiness.
This event – narrated by Ovid in Metamorphoses (book II,vv. 19-102) – is presented in a very spectacular way on a vast blue sky that seems to break through the vault’s real architectonic consistency and warns against depending too much on one’s strength in dealing with demanding undertakings: in the case of the Prince-Bishop and governments in general, the reference is to political responsibility, for which wisdom and prudence are indispensable virtues. Phaeton’s speeding chariot also alludes to the .passage of time, marked by the seasons that follow one another, across the vault from east to west following the actual path of the sun in respect to the cardinal points. Positioned at the extremes of the vault are the allegorical figures of the Sun (Apollo – day) and of the Moon (Diana – night) that recall these cardinal points. Next to them in the smaller panels, are the personifications of the seasons: Spring and Summer to the east, with their fruit and flowers, and to the west, Autumn and Winter, with grape bunches and dry leaves.