At the foot of Zagros Mountains, there is a city called Shushtar, capital of Khuzestan, Persia, which owes much of its fame to the historical hydraulic system located there. Inscribed as a masterpiece of creative Genius by UNESCO world cultural heritage organization can be traced back to Darius the Great I, king of kings   , king of Achaemenid dynasty in the 5th century B.C. 

The historical complex of mills and waterfalls of Shushtar could be more used at Sassanid era and are still healthy after 1500 years. The water structures of Shushtar have been built exploit the waterpower for mills. The complex consists of different parts such as mills, waterfalls, canals, aqueducts, and "Sika" a recreational place.

Shushtar Historical Hydraulic System is still in use providing water to the city of Shushtar via a series of tunnels that supply water to mills, which forms a spectacular cliff from which water cascades into a downstream basin.

In Shushtar Historical Hydraulic System there are 2 main channels that pass through the Karun River. Over the centuries, one of these channels, called Gargar, continues to provide water for the residents of Shushtar through several tunnels.

The main task of Shushtar historical hydraulic system is to block the Gargar river, so that the surface of the water can be used to drain the tunnels in the slate. Gargar tunnels provide water for residents of the area through the transfer of water from their passageways.