Its earliest capital was at Dara and later moved to Hecatompylos.  
The founder of this empire had been a governor under Diodotus.  Its earliest capital was at Dara and later moved to Hecatompylos.  It was eventually overrun by the Sassanids, who took its city of Ctesiphon for their own capital.  Conquered in 226 A.D. by Artaxerxes, it had existed for almost 500 years from when Arsaces I liberated it from the Seleucid Turks in 247 BC.  FTP, name this Asian empire between the Euphrates and Indus Rivers that probably took its name from the name for ancient Persia, which was Parsa.
The founder of this empire had been a governor under Diodotus.  
Parthia or Parthian Empire