The kingdom of the Seleucids was in fact the successor of Alexander's empire, and as a result of that the indirect successor of the Persian empire. It was the most heterogeneous of the Hellenistic kingdoms because of its enormous size and diversity of nationalities. That is the reason why the Seleucids could not exploit the land as was it their personal possession like the Ptolomies did. However, they did have the same principle as the Ptolomies: centralisation, organised exploitation, and state-monopolies were pursued. Still, trade was free unlike as in the kingdom of the Ptolomies, with the exception of the unavoidable royal taxes.

There was a difference between Asia Minor and Syria-Mesopotamia where the government directly controlled the people, and the highlands of Iran where the royal house had to face the very powerful local nobility. Especially there remained the Persian systems of satrapies unchanged. The political centre of the Seleucids was situated in northern Syria and Asia Minor while their main interests where in the Aegean. One of the most remarkable aspects of their civilisation was the high standard of urbanisation. They founded numerous Greek colonies, ranging from agricultural settlements with a military character like Egyptian cleruchies till full Poleis.

In northern Syria they founded four cities. The residence Antioch, situated at the river Orontes, became the Alexandria of the kingdom of the Seleucids and grew into an immense city. South of Antioch was the most important military base Apamea, and at the coast you could find the harbours Seleucia and Laodicia. Another city was founded at the Tigris: Seleucia Tigris. This city became the second capitol of the kingdom and replaced Babylon as centre of the east-west trade. The old city now fell into decay quickly and for good.