The Lycurgus Cup. 4th Century AD. Romano-British
This drinking cup is made of dichroic glass, which shows red or green depending on which way the light passes through it.
The cup depicts the torment of King Lycurgus, who incurred the wrath of Dionysus by banning the cult of the god. In the ensuing madness the deity had cursed Lycurgus with, he killed a nymph (and follower of Dionysus) named Ambrosia, who was transformed into a vine. She can be seen wrapped around the king on the glass, restraining him while Dionysus and his followers look on.
The cup may have been designed to be used at Bacchic cult celebrations, the popularity of which was still a feature of Roman religious life around 300 BC.
The Lycurgus cup is the only complete (although cracked) Roman object of this particular type of glass, and the shift from red to green is one of the more impressive extant colour shifts.