Babak Fortress, also known as the Immortal Castle or Republic Castle, is a large citadel on the top of a mountain in the Arasbaran forests, which is located 16 km southwest of Kalibar City in northwestern Iran, East Azarbaijan Province.
The fortress was built during the Sasanid dynastic era; however it is famous for the 23 years residence (816 to 837 CE) against the Arab invaders by Persian hero Babak -e- Khoramdin and his warriors. Eventually Babak, his wife, and his warriors were forced to leave their command post at the castle under very difficult circumstances. He was betrayed and was handed over to the Arab invaders.
Every year at the last week of June (At first week of summer by Iranian Calendar) Babak’s birthday symbolically is celebrated at the castle.
The Babak Fortress, a unique heritage of the province, was built on 2300-2600 meter heights, with valleys 400-600 meters deep all around. The architecture of the building resembles that employed in the building of Takht’e Soleiman historical complex in the neighboring West Azarbaijan which was built in the Sassanid era Just one narrow dusty road leads to the fortress, and to reach it one has to pass a temple along a 200 meter hallway. Despite its harsh access route, the citadel has unique natural characteristics as the region’s mountainous features can be one of the most important factors drawing people to the site.
The citadel houses two two-story and three-story buildings. Its main hall is surrounded by seven connected rooms. To the east of the fortress, there are a number of rooms and water reservoirs. In winter, the reservoirs would be filled with rain and snow and used in times of trouble such as when under siege. The internal building of the citadel comprises a hall, four rooms connected to it, an entrance and a place for soldiers.