Shushtar is one of the oldest cities of Iran which is located in Khuzestan Province and crosses the large river Karun (in past, people called Pasitigris). At the 2012 census, its population was 192,361. It is an ancient city that is situated at the foot of Zagros Mountains, approximately 92 kilometers (57 miles) away from Ahvaz, the capital of the province. Archeologists considered some old tools such as knives, spears, and Etc that have been found there, also they believed that human inhabited in this land about 7000 years ago. In addition, During the Sassanian era, it was an island city on the Karun River and selected as the summer capital. Shushtar infrastructure included water mills, dams, tunnels, and canals that Gar Gar weir was built on the watermills and waterfalls. Bolayti canal is situated on the eastern side of the watermills and waterfalls that the functions are related to supply water from behind the Gargar Bridge to the east side of watermills and the water of the river in order to prevent damage to the watermills. This system (Shushtar Historical Hydraulic System) has been registered in UNESCO’s list of World Cultural Heritage Sites in 2009, referred to “as a masterpiece of creative genius.” This city has a hot semi-arid climate with extremely hot summers and mild winters. Rainfall is higher than most of southern Iran. Furthermore, Shushtar New Town is one of the most well-known housing projects in contemporary Iranian architecture.