Abstract
The expansion of the Seleucid realm in the east and its need to dominate the Iranian people led to the creation of pro-Greek bases by forcing its Greek-Macedonian subjects to emigrate into the eastern lands. The construction of new colonies along the eastern trade routes and their politico-economic performance strengthened the Seleucid rule and made it more enduring than the Macedonian empire of Alexander the Macedonian. The existence of Hellenistic colonies in Central Asia led to the sending of large numbers of Greek-Macedonian immigrants to the region, which themselves opened a new window on Eastern-Western trade. Based on the archeological data and historical texts and using the descriptive-analytical method, the present article intends to clarify the nature of Seleucid urban planning and the difference between colonies and poleis. Then it will explain the reasons for the creation and function of colonies in Central Asia and the Iranian plateau. Since the focus of previous research has been more on how to build and rebuild Seleucid cities in Syria and Asia Minor, the present study seeks to focus on the question of why the Seleucids intended to build different colonies and cities. The research hypothesis is that the Seleucids, in addition to their military use of these cities, also considered their economic use, especially when one can see that these colonies, which later became large cities, were located along the eastern trade routes, which played an economic role. 
Keywords: Seleucids, Urbanism, Polis, Colony.

Introduction
During the rule, the Seleucids ruled over a wide range of civilized lands in the ancient East, and in the broadest sense, they controlled the borders between Polis and Syria. They established colonies and Polis to gain more control over their open lands and to build popular bases in these lands to strengthen their power bases in the lands that previously belonged to the Achaemenids. Formating. the idea of colonizing and creating barracks, there is a legacy of Alexander the Great during the time of his conquests, which was the import of digital and social construction of the liberated lands. The arrival of Ionian-Macedonian immigrants in the area between Mesopotamia and the ancient East was a turning point in the culture and civilization of Hellenism during its lifetime. In a way, the center of gravity of the Hellenistic base is transferred from the west of the ancient world to the eastern part, and until the last days of the life of the Hellenistic empires in Syria and Egypt, it is necessary to try to survive.
The active presence of the Polis in the rise to power or overthrow of the Parthian emperor’s Citizenship or disobedience to the commanders of the Roman civil war and the Polis and then their lives in the time after the most important Seleucid heritage in the east of the budget. Therefore, the present study aims to first clarify the nature of colonies and Polis and then answer a few questions about them. Among the policies of colonization and urban planning (Polis) in the Seleucid Empire, have they been carried out on a planned basis or not? Has the Khorasan road been a clear trajectory for the establishment of a colony? Did the location of the colonies and the Polis play a role in the creation of trade roads in later periods?

Conclusion
The Seleucid emperors faced many problems during their lifetime, including the heterogeneity of tribes in the vast geographical region of their rule. An important part of the protests and revolts against this non-Iranian dynasty was the non-indigenousness of these people. Although Seleucus the 1st  tried to eliminate this position of the Iranian tribes towards himself by choosing Antiochus I, an Iranian mother, as his successor, but as we have seen, he did not succeed much. The Seleucid emperors found a way out of this situation by establishing popular bases within their lands. He took the first step to legitimize himself by establishing colonies and migrating the Greek-Macedonian population to these places throughout his lands. The Seleucids, with a clear understanding of the position of the colonies from a Geo-political and Geo-economic point of view (Geo-economics) in the lands under their control, sought to strengthen and expand some of these colonies to establish stronger bases for themselves in Although in some places, such as Central Asia, the weakening of the Seleucid government was accompanied by the declaration of independence of the Central Asian Polis from the Seleucid Empire, in some areas the Seleucids had better control over those areas. The Polis and Polis remained under their yoke, although with the collapse of the Seleucid regime in Iran, the colonies gradually dismantled or became a small town, for many years the Hellenistic Polis played a key role in Iranian politics. Thus, the undeniable role of the colonization policy in the ups and downs of the Seleucid government can be considered and it was concluded that with the decline of the importance and credibility of the colony, the Seleucid government lost its strategic base and the rhythm ended. The lifespan of this dynasty intensified.