Papak Fort or Babak Castle , also known as the Immortal Castle or Republic Castle , is a large citadel and National Symbol of Iranians on the top of a mountain in the Arasbaran forests , which is located 6 km southwest of Kalibar City in northwestern Iran . It has been identified as the stronghold of Papak Khorramdin , the leader of the Khurramites in Azarbaijan who fought the Islamic caliphate of Abbassids . Iranian Azarbaijanis gather at Babak Castle during the first weekend in July for the annual commemoration of Babak Khorramdin .
The ascent to the Castle is not for the infirm , elderly , or those afraid of heights . A series of long , and in places , broken steps lead the traveler to the top of a hill from where there are several choices for further ascent . The easiest is straight in front of the steps and consists of a long dirt track . As there are no sign posts towards the Castle , walk towards the peak on your left hand side but do not leave the dirt track . You will need hiking boots , a sun hat , plenty of water , and at least 3 hours for the climb , and 2 hours for the descent .
At the end of the dirt track , turn left onto the rocky mountain side , and beware of slipping . The first of sign of the ruins will appear on your left , but do not become too complacent : the actual Castle is another 2 peaks march away . The first peak offers spectacular views of the Castl . After ascending a second peak , with its own ruins , you will see the Castle perched on top a jagged cliff . Ascending the Castle steps is a dangerous process , as there are sheer cliffs on your right hand side , and no protective rails or fences to prevent a fall of several hundred meters . Take extreme care of the edge , and hold on to your children .
Once you have climbed the pinnacle of the cliff , you will truly appreciated the amazing effort in building and maintaining a fort at this altitude . Unfortunately , you will also have to tolerate the graffiti on the ancient walls , and young people playing chicken on top of the Castle walls . Under no circumstances should you even consider climbing these walls : first , this can damage the ancient structure , and second , a fall of several thousands of meters would lead to certain death . Nevertheless , the experience afterward is well worth the strenuous climb : the surrounding Arasbaran oak forest , jagged cliffs , mountains in the distance , and the history of the place combine to create one of Iran's most beautiful vistas .
The castle , built on 2300-2600 meter heights , surrounded by gorges as deep as 400 to 600 meters , is believed to belong to the Parthian dynasty and modified under the Sasanid dynasty . To reach the castle , one has to trek a tortuous and narrow passageway and then cross a corridor-shaped temple , 200 meters in lengths .