Alexander the Great conquered Persia in 331 B.C. and ended the Achaemenid Empire founded by Cyrus the Great. For the next five centuries, the Iranian plateau became ruled by other empires, until a new Persian dynasty took power. Fiercely proud of their roots, these new kings—the Sassanians—restored the might of their ancestors, drawing on their past to become feared conquerors, grand builders, and artistic patrons.
For more than four centuries the Sassanians dominated western Asia, expanding their empire and gaining lands from the Roman and Byzantine empires in the west and the Kushan empire in the east. To strengthen their connection to the past, they honored their leaders by carving reliefs of their deeds at Naqsh-e Rostam, the traditional resting place of the Achaemenid kings. Zoroastrianism became the state faith, and the government became centralized.
Sassanians grew wealthy, enriched by the trading routes (including the Silk Road) that passed through their realm. Centered in what is now Iran, the Sassanian empire was home to diverse ethnicities and cultures. It was known for its libraries, vast centers of learning, and soaring achievements in monumental art and architecture. By looking backward, the Sassanians moved their culture forward.