The Persian Empire was vast - the largest that the world had ever seen. It encompassed for much of its history all or most of Iran, Iraq, Syria, Jordan, Israel, Lebanon, Egypt, Turkey and Cyprus, along with parts of Afghanistan, Pakistan, Turkmenistan, Uzbekistan, Armenia and Greece.

Despite this, administration of the empire was efficient. At its heart was the great king and his court. His territory was divided into provinces (satrapies), each controlled by a governor (satrap) or 'protector of the realm'. The institution began with Cyrus until under Darius there were about twenty satrapies. The satraps were Persian nobles, often relatives of the king, and their loyalty had to be absolute.

The subject peoples were many and varied, with some inhabiting cities and others living tribal, nomadic lives. However, despite its all-powerful ruler, the empire was inclusive and tolerant of different languages, religions and cultures.