The first and the greatest Persian empire in the world was the Achaemenid empire, founded in 550 BC by Cyrus the great, the grandson of the last Median king, Astyages.The territory of this empire extended from North Africa in the west to India in the east and from Jaxartes River in the north to the Persian Gulf in the south.
They had several capitals in Iran such as Ecbatana, Susa, Pasargadae and Persepolis (the ceremonial center) the remnants of which is the most important and the most magnificent historical site in Iran, registered by UNESCO and of course, the main destination for all tourists.
As Cyrus, the great was Persian on the father’s side and Median on the mother’s side, he founded the Achaemenid Empire based on the unity of the Persians and the Medians while all other races and nationalities were accepted and respected as well. The empire was based on tolerance and freedom of races and religions.
When Cyrus the great founded the Achaemenid Empire, he started the construction of Pasargadae on a fertile and green land, as his capital and ordered the construction of a complex of palaces including the private palaces and audience halls. Today the ruins of Pasargadae in Fars province are registered by UNESCO as a world cultural heritage site. After Cyrus the great his elder son, Cambyses ascended the throne and ruled over Iran for a short while. He conquered Egypt and either died or got killed on the way back to Persia (Iran).
The next successor was Darius the great. It was during the reign of this king when an efficient road system was developed to reduce the time of message delivery from 3 months to two weeks. By the order of Darius the great, the construction of Persepolis was started in 518 BC and continued during the whole Achaemenid era and it was not finished until 330 B.C. when Alexander the Macedonian attacked Persia and burnt it into ashes.
The successor of Darius the great was his son, Xerxes, who made the most unwise decision by putting Athens on fire and so, causing a deep hatred and grudge in the hearts of the Athens which finally led to the catastrophic destruction of Persepolis by the Greeks. The other Achaemenid kings were Artaxerxes I, Darius II, Artaxerxes II, Artaxerxes III and the last of the Achaemenid kings was Darius III who fled to Ecbatana when Alexander attacked and surrendered the whole empire to the Greeks.