One of Iran's most impressive fortress-citadels, the Arg's vast adobe walls top a gentle slope directly south of central Rayen. Inside is a castle within a castle. Some sections are very ruinous but wandering through the extensively restored governor's quarters it's easy to imagine the trepidation that supplicants must have once felt approaching the powerful local ruler through dark passages and hidden inner courtyards.
Superb views from the battlements above the gatehouse reveal a backdrop of Mt Hezar (4420m).
The exact age of the arg is unknown, though it's thought to be well over 1000 years old. Until restoration in 1996 it had been essentially abandoned for about 150 years.