Tomb of the Julii, Ancient tomb in Vatican Necropolis, Vatican City.

The Tomb of the Julii, or Mausoleum "M", is a vaulted burial chamber in the Vatican Necropolis beneath St. Peter's Basilica. Its ceiling mosaic, dated 266 CE, sets a haloed solar deity driving a chariot among yellow and gold tiles, framed by green vine scrolls with leaves and clusters. Dark tiles outline a draped figure on the left and, below it, an animal with a rider.

Workers uncovered this burial chamber by chance during construction work near the basilica in 1574. The entrance was then sealed, keeping the tomb hidden from public view for several centuries.

The vault mosaic shows a solar deity with an aureole in a chariot, framed by vine scrolls; the same vine motif is read through John 15:1 rather than its usual Dionysiac sense. Other mosaics depict Jonah and the whale, the Good Shepherd carrying a lamb, and fishermen, which led to the tomb being interpreted as an early Christian vault.

Access is only possible through guided tours of the necropolis organized by the excavation office. Daily visitor numbers are strictly limited, so booking in advance is strongly recommended.

The vault mosaic dates to 266 CE, making it the earliest known depiction of Christ in the guise of the sun god, an identification argued by Allen Brent. The tomb itself was built for Julius Tarpeianus and his family, as a now-lost doorway inscription recorded.