The room takes its name from the "Cabinet of the Sun-Dial", which existed here prior to the reconstruction of 1920-1925, thus named on account of a sun-dial set into the floor, of which there remains only the fragment on display. On the walls there are the original panels of the sixteenth-century windows, decorated with landscapes and grotesques, partly repainted in the eighteenth century with geographical and astronomical annotations. These latter date from the moment in which the apartment was inhabited between 1780 and around 1798 by the cardinal librarian Francesco Saverio de Zelada (1717-1801), secretary of State under Pope Pius VI. His collection was arranged here, and included physical and astronomical instruments and a museum of naturalism as well as antiquities and paintings.
The display includes Attic vases dating from 490 to 350 B.C. and vases of Etruscan production from around 480 to 300 B.C.
With regard to Attic ceramics, it is possible to trace the development of Athenian vase painting through the work of the masters active between the first decades of the fifth and first half of the fourth century B.C.
From a stylistic point of view, it is the transition from the late severe style to full classical style that constitutes the central theme of the room. Finally, with the subsequent late classical-style production, the centuries-long history of Greek ceramic painting reached its end.