Pars Sea: Southern Border of Iran in Ancient Times

The present paper investigates the natural borders of Iran with an emphasis on the southern border, Pars Sea or the Persian Gulf. In the history of ancient Iran, it functioned as a natural obstructive element against the foreign power's invasion of the plateau of Iran and played an important role in the development of commerce. In order to discover the reasons of the attention of ancient Iranian governments to Pars Sea, it is necessary to study the geographical status of Iran, which, like a bridge, connected several ancient eastern and western countries to each other. At that time, in order to fortify political borders, it was necessary to match them with natural borders. Having access to the southern border of the country was of great importance to Iranian rulers because it would enable them to stabilize eastern and western trade routes and develop international trade in the course of their political and economic competitions with Greece and Rome. In fact, Iran's supervision over Pars Sea was in line with its dominance over sea trade highways and maintaining the power balance in the region. Finally, the importance of the south of the country in the religious thoughts of Iranians, particularly during the Sassanid era, highlighted its supreme station as the abode of gods.