It formed the southwestern administrative division of Pars, and consisted of a mountainous countryside of the southern Zagros Mountains-much of the territory inhabited later by the Qashqai tribe; with its mountainous terrain and extreme temperature, this was regarded by the geographers as a "sardsīr" (cold zone).
Istakhr (Middle Persian: Staxr) served as an administrative and religious centre under the Sasanian Empire, which it had done since Achaemenid times.