This hydraulic system is an interconnected complex of mills, waterfalls, bridges, dams,  channels, huge water conduction tunnels and Sika (a Leisure place) which work together in order to optimize the use of water power as the driving force of  industrial mills.

The system distributes the Karun water to all regions of Shoushtar and the cities around. All areas of waterfalls and mills were built of Granite and lime mortar, and the material of making nesting rooms was carved stones and also stone walls of the river.

The work process of Shoushtar complex based on the Gargar dam (which itself is one of the engineering masterpieces totally hand-dug in Sasanid era) blocks the river flow and consequently raises the water level in order to dewater three tunnels dug in the rock.

Triple tunnels direct water into several channels, turning the mills' wheels, as water pours into a pool-like area, like a waterfall.

Source: Visitiran.