Bishapur: important Sasanian city in Iran, founded by king Shapur I, and built by Roman POWs.
The badly damaged first relief of Bishapur, in the Tang-e Chowgan gorge, shows the investiture of Shapur. We can see still recognize many elements, and because Sasanian investiture reliefs are often a bit stereotypical, we can deduce the rest.
Essentially, this monument is a copy of a relief made by Shapur's father Ardašir I (r.224-241) at Naqš-e Rustam. Two horsemen are facing each other. From the left, the supreme god Ahuramazda hands over the symbol of power, the cydaris ring, to Shapur, to the right. Ahuramazda's horse tramples upon the devil (Ahriman), whereas the horse of Shapur steps on the body of the Roman emperor Gordian III, who died during his campaign against the Sasanian capital Ctesiphon (244). The central, kneeling figure is the emperor Philippus Arabs, who paid a large ransom and was allowed to take back the remains of the Roman army.
In 260, Shapur defeated another Roman emperor, Valerian. Although our relief is damaged, we can be certain that he was not depicted. Therefore, this monument was made between 244 and 260. The defeat of Valerian necessitated the creation of a new monument.
Louis Vanden Berghe, Reliefs rupestres de l' Iran ancien (1983 Brussels), #59.