Settling in a country with vast areas of arid or semi-arid lands has been one of the biggest challenges overcome by the Iranians throughout history. Darius the great had two canals divert the water from Karun river to irrigate an area of 40,000 hectares called Mianab, in the southwest of Iran. The system consists of a room where the entire system was operated and controlled, a tower, mills, basins, damns and the Salasel Castle. The site was recognized as a UNESCO World Heritage Site in 2009.