Shushtar hydraulic system, one of the oldest engineering masterpieces in Iran and the world, has been constructed as an economical-industrial complex in the vicinity of the Shushtar historical area, under Sassanid Empire.
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 optimal use of water power as the driving force of industrial mills. The system distributes the Karun water to all regions of Shushtar and the cities around. All areas of waterfalls and mills was 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 Shushtar complex based on the Gargar dam (which is itself one of the engineering masterpieces totally hand-dug in Sasanid era) which 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, water pours into a pool-like area, like a waterfall.