Description : Shushtar Historical Hydraulic System is an island city from the Sassanid era with a complex irrigation system situated in Iran's Khuzestan Province. It has been registered on UNESCO's list of World Heritage Sites in 2009 as Iran's 12Th cultural heritage site to be registered on the United Nations' list. The Shushtar water mills ones are the best ones which operation in order to use water in ancient periods. These include a collection of dams, tunnels, ancillary canals watermills which utilized as Industry–Economic collection. GarGar was built on the watermills and waterfalls that abstracted on storm the GarGar branches and have function similar of up to date dams to lead the water in the tunnel of watermills. Bolayti canal is situated in eastern side of the water mills and water falls and the function of this canal is to supply the water from behind the GarGar bridge to the east side of water mills and the channel the water of river in order to prevent the damage to the water mills. Dahaneye shahr tunnel (city orifice) is one of the three main tunnels which channeled the water from behind the GarGar into the water mill and then run several water mills. Seh Koreh canal channels the water from behind the GarGar bridge into the western side. In water mills and water falls, there are noticeable mills we can see a perfect model of haltering to run mills. The Band-e Kaisar an approximately 500-metre long Roman weir across the Karun was the key structure of the complex which along with the Band-i-Mizan retained and diverted river water into the irrigation canals in the area. Built by a Roman workforce in the 3rd century AD on Sassanid order it was the most eastern Roman bridge and Roman dam and the first structure in Iran to combine a bridge with a dam. Parts of the irrigation system are said to originally date to the time of Darius the Great the Achaemenian king of Iran. It partly consists of a pair of primary diversion canals in the Karun river one of which is still in use today. It delivers water to the City of Shushtar via a route of supplying tunnels. The area includes Selastel Castel which is the axis for operation of the hydraulic system. It also consists of a tower for water level measurement along with bridges, dams, mills, and basins. Then it enters the plain south from the city where its impact includes enabling the possibility of farming over the area called Mianab and planting orchards. In fact the whole area between the two diversion canals (Shutayt and Gargar) on Karun river called Mianab an island having the Shushtar city at its northern end. The site has been referred to as a masterpiece of creative genius by UNESCO.