The Shushtar Hydraulic System in the island city of Shushtar is a complex irrigation system that dates back to the time of the Achaemenid king Darius the Great in the 5th century BCE. Described by UNESCO “as a masterpiece of creative genius”, the Shushtar Hydraulic System involved the creation of a diversion canal on the river Karun to form a moat around the city, over which bridges and gates were built to keep away unwanted visitors. A system of subterranean channels called Ghanats connected the canals to the private reservoirs of houses, buildings and watermills. These tunnels supplied water for domestic use and irrigation, as well as to store and supply water during times of war when the main gates were closed. Although this complex system of irrigation degenerated during the 19th century, traces of the Ghanats can still be found in the crypts of some houses.

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