Zoroastrians are the oldest remaining religious community on the Iranian Plateau. Prior to the Muslim conquest of Iran, Zoroastrianism was the primary religion of Sassanid Iran. According to the country's official census, there were 25,271 Zoroastrians in the country as of 2011, but some unofficial accounts suggest higher figures. Background There are no impartial written records from Zarathushtra's time. The earliest surviving written references to Zarathushtra (from non-Iranians) seem to be those of Greek writers. Zarathushtra and his first followers were Iranians that lived between the Bronze Age and Iron Age (est. 1200-600 BC). The time of the Iranian peoples' migration to Iran can be mainly estimated through Assyrian records. Also, Herodotus (I, 101) recalled one of the Mede tribes to be called "Magoi", better known as "Magis", a tribe known to have included many priests, who served both Medes and Persians. By the time of the Median empire (est. 612 BC), Zoroastrianism is known to have been well established in both the Pars region (later capital of Persia) as well as in the Eastern regions. Achaemenid dynasty Persians led by Cyrus the Great soon established the second Iranian dynasty, and the first Persian empire by defeating the Medes dynasty in 549 BC. As Persians expanded their empire, Zoroastrianism was introduced to Greek historians such as Hermodorus, Hermippus, Xanthos, Eudoxus and Aristotle; each giving a different date regarding the life of Zoroaster but naturally believed him to be a Persian prophet and called him "Master of the magi" Although there are no inscriptions left from the time of Cyrus about his religion, the fire-altars found at Pasargadae, as well as the fact that he called his daughter Atossa, name of the queen of Vishtaspa (Zoroaster's royal patron), suggests that he indeed may have been a Zoroastrian. However, it is clear that by the time of Darius the Great (549 BC– 485/486 BC), the empire was clearly Zoroastrian. Darius declares in one of his inscriptions that: Persepolis Persepolis (or Parsa) was one of the four capitals of the Achaemenid empire, built by Darius the Great and his son Xerxes; it was a glorious city known to the world as the "richest city under the sun". It was also the trading capital of the Near East. One of the main functions of Persepolis was to serve as the host of the ancient Zoroastrian festival, Norouz. Therefore, every year representatives from each country