The sources for the Grecian Urn

The Borghese Vase in the Daru Gallery, at Louvre Museum

Drawing of the Sosibios Vase, by John Keats, Keats-Shelley Museum, in Rome

The Portland Vase

Perhaps from Rome, Italy, about AD 5-25
The most famous cameo-glass vessel from antiquity
The scenes on the Portland Vase have been interpreted many times with a historical or a mythological slant. It is enough to say that the subject is clearly one of love and marriage with a mythological theme. The ketos (sea-snake) places it in a marine setting. It may have been made as a wedding gift. (British Museum)
   

The Townley Vase, Roman 2nd century AD (British Museum). Found at villa at Monte Cagnolo near Rome

Sosibios, The Athenian Volute krater c 50 BC (Musée du Louvre)