The Portland Vase, housed in the British Museum, is the most important surviving example of “cameo glass,” datable to the early years of the Roman Empire. Until 1909, there was no doubt regarding the provenance of the vase. It was said to have come from the sarcophagus with scenes from the story of Achilles discovered in 1582 inside a large burial mound, the so-called Monte del Grano, which still stands at the fourth mile of the via Tusculana. However, in 1909, Henry Stuart Jones ruled out this provenance. The re-examination of the monument, which should be identified as the tomb of Alexander Severus, shows that the report of the provenance of the vase from the Monte del Grano sarcophagus is authentic. Similar conclusions can be reached from a re-examination of the vase itself, which suggests the two myths it depicts should be identified as the wedding of Peleus and Thetis and the afterlife of Achilles.