The earliest examples of visual representations in Iranian history are traced back to the bas-reliefs of Persepolis, c. 500 BC. Persepolis was the ritual center of the ancient kingdom of Achaemenids, and the figures at Persepolis remain bound by the rules of grammar and syntax of visual language. The Iranian visual arts reached a pinnacle by the Sassanid Era. A bas-relief from this period in Taq Bostan depicts a complex hunting scene. Similar works from the period have been found to articulate movements and actions in a highly sophisticated manner. It is even possible to see a progenitor of the cinema close-up in one of these works of art, which shows a wounded wild pig escaping from the hunting ground.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): In what era did Iranian visual art reach its peak?
the Sassanid Era