Dehdasht City in Kohgiluyeh and Boyer-Ahmad Province is limited in the north by Baq-e-Malek, Eazeh (Khuzestan province) and Lordegan (Chahar Mahal Va Bakhtiyari province) and in the south by Gachsaran, in the west are the cities of Behbahan and Ramhormoz (Khuzestan province) and in the northeast is Boyer Ahmad. This city has two kinds of climate that are quite different. A cold region and a tropical region providing winter-quarters for tribes.
Sometimes in summer it is even cold in the summits of the mountains, whereas, warm weather prevails in the southern areas. This region has lots of mountains, where there are residential facilities. Aryobarzan the Achaemenian commander in Takab a narrow pass of this region (in northeast of Behbahan) resisted against the army of Alexander the Macedonian.
In a place called Tang-e-Sorook ancient constructions can be observed such as stone stairs and a statue, alongside a route related to the Sassanide period. The city of Dehdasht which is the center of Kohkiluyeh, in the past was one of the trading centers of Fars, Esfahan and Khuzestan provinces. In the Sassanid era , Qobad Sassani founded Arjan the present city of Behbahan, in the plain regions which was known as Qobad Khoreh.
The mountainous regions were also called "Rome Zemigan". In the post Islamic period Qobad Khoreh, was called Argan or Arjan and the mountainous region of "Rome Zemigan" was reputed as Kohkiluyeh. In later centuries when Arjan turned to ruins and was triumphed by the Afshar and Lors, most of this territory was called "Kohkiloyeh", its mountainous region "Posht Kooh" and its plain was called "Zir Kooh". Kohkiluyeh is one of the flourishing and developing townships of the province today.