Dena the tallest and largest is the Zagros Great Range and has a roughly 90 km long line between three province Kohgiluyeh and Boyer Ahmad , Isfahan and Fars. The Dena mountain range has a peak of 4,000 meters and the highest peak of 4,000 meters in Iran belongs to this mountain range.
Dena is not a peak, but a mountain range from the northwest to the southeast, divided into three main courses and a vertical sub field, by the three bridges of Bijan, Morgol, and Potak.
Dena begins 20 kilometers east of Yasuj and extends up to 70 kilometers northwest. This mountain originates from the northwest (Keta village) and extends to the southeast (Kakan area), which is more than 80 km long and has an average 15 km. The highest peak of the Dena mountain range, Bijan Peak (Qashmestan), is 4409 meters high and is 35 kilometers northwest of Yasuj. City of Sissokhat, Dena city center is located in the hillsides of this mountain. Due to the length and high altitudes, annual rainfall in this mountain varies from 600 to 1800 mm, and a number of rivers flow from it.
Among the rivers that originate from this summit are Bashar, Khersan, Reagan, Marbur, Mehriyan, Mount Gol, Diashm, Seris, Tizab and Dzhkerd.