Shushtar, Historical Hydraulic System, inscribed as a masterpiece of creative genius, can be traced back to Darius the Great in the 5th century B.C. It involved the creation of two main diversion canals on the river Karun one of which, Gargar canal, is still in use providing water to the city of Shushtar via a series of tunnels that supply water to mills. It forms a spectacular cliff from which water cascades into a downstream basin. It then enters the plain situated south of the city where it has enabled the planting of orchards and farming over an area of 40,000 ha. known as Mianab (Paradise). The property has an ensemble of remarkable sites including the Salasel Castel, the operation centre of the entire hydraulic system, the tower where the water level is measured, dams, bridges, basins and mills. It bears witness to the know-how of the Elamites and Mesopotamians as well as more recent Nabatean expertise and Roman building influence.