The first Iranian independent government which was established under the Seleucid rule (250 B.C.), is called Arsacid Dynasty in the Persian language because the name of their first king was Arsac. After unifying their power the Parthian kings expelled the Seleucid rulers and built a new big Iranian empire, the sixth in size in the ancient world. The only enemy during their rule was Rome. The Parthian dynasty was governed by 29 Kings and about 470 years.
Parthian golden necklace, 2nd century AD, Iran, Reza Abbasi Museum
During the Parthian Period trade expanded from Syria and Phoenicia in the west to India and China in the east. Their area was attacked by barbarian invaders and they had different wars with them. These wild groups harassed the Parthian country from the east toward the west. The Parthian government's system was very new because! they had two consultative parliaments. One! parliament was composed of princes and nobles! and the other by priests. The two parliaments limited the royal authority and the kings did not possess absolute power.
The first Parthian capital was probably at Dara which today is called Abiverd, Hecatompylos, one of the most recent capitals, was probably close to the modern Dāmghān city. The empire was on governed by a small Parthian aristocracy who used the social organizations established by the Seleucids successfully, and who endure the development of vassal kingdoms. The Parthians controlled most of the trade roads between Asia and the Greco-Roman, and this control provided them a great wealth that they used for their vast construction activities.