Concurrent with the construction of the huge Karun-3 Dam and the sinking of the communication axis of Khuzestan and Chaharmahal and Bakhtiari provinces, the construction of an alternative road began at a height above the dam lake level. Following the construction of the road, two all-metal arched bridges were designed above the dam on a valley about 250 meters deep. And then due to the impassability of the area, great depth and slope on both sides of the valley, the impossibility of using temporary foundations and other common installation methods, two cranes with a capacity of 20 tons each with a weight of 70 tons each were designed and transferred to the desired location to build up the bridge. Arak Machine Building Company successfully completed the design, construction and installation of this bridge in 20 months. The Karun-3 Arched Bridge is the largest arched bridge in the Middle East.