The Koohrang Tunnel is situated near Chelgerd in the Chaharmahal and Bakhtiari Province and it is said that it was constructed so as to annex the waters of Koohrang to that of the Zayandeh Rood. The construction of the tunnel began during the Sassanid period, approximately from the time of Shah Abbas I. At the time they planned to make a vertical crevice at the vertical axis of Karkonan Mountain and by means of a dam which crosses the same axis, lead the water through the crevice to increase the water level in Karoon River. Although first proposed in the early sixteenth century, the Koohrang Tunnel was finally completed in 1953.It should be clarified though that while this waterway is called a tunnel, however, for the most part it is not really a tunnel in the sense that it has no roof, but rather is an open waterway or water canal. Along its path there is also a waterfall which gives the area a very scenic view. Throughout the year, even in the winter as a result of its proximity to ski slopes, many tourists can be spotted enjoying this natural environment.In recent decades the new tunnel of Koohrang was constructed joining the 3 water branches of the Karoon River to 3 water branches of Zayandeh Rood and therefore has created an interesting vicinity worth seeing. Two additional tunnels were constructed in late 1990s and early 2000s. Throughout its course, the presence of lush green thickets adds to the beauty and the pleasant environment, which attributes to the recreational atmosphere.