When Vesuvius erupted in 79 CE and buried Pompeii, it also sealed the so-called 'Room of the Mysteries' in a villa about a kilometre beyond the city's northwest gate. Excavated in 1909, the room emerged with all four of its painted walls intact: a cycle of twenty-nine over-life-sized figures running unbroken around the space. The frescoes decorated a side room, not the villa's grand hall — yet their scale and technical command are unmatched in surviving Roman painting.

The scenes are still argued over. The most common reading interprets them as the staged initiation of a young woman into the cult of Dionysos, the mysteries: a reading of sacred text, a frightening apparition, the lash of a winged figure, and finally a ritual dance. Other readings see a wedding preparation, an oracular scene, or the secret teaching of the Bacchae. Whichever account is taken, the frescoes preserve the visual record of an ancient ceremony.

Technically the cycle is the high point of Roman 'Second Style' wall painting: the ground — Pompeian red — is treated less like a painted surface than like the back wall of a stage in front of which the figures stand. The shading, expressions, and sense of arrested motion preserve, through Roman hands, a Greek tradition of large-scale painting almost entirely lost in the original.