This river is the biggest river in Iran. It is 890 kilometers long, hence, being the longest river. The Karun rises from springs in the Vang mounts and from the Zard Kuh Bakhtiyari mountains. It rises from the eastern valley of Zard Kuh (known as Kubrang) and flows down towards southeast. It flows past Shahr-e Kurd, Brujen, Lurdgan, Izeh, Masjid Soleyman, Shushtar, and Ahwaz to Khorramshahr. In the east of Khorramshahr it divides into two branches. The eastern branch, known as Bahmanshir, flows toward southeast and goes to the Persian gulf through Khor Mosa. The western branch flows past south Khorramshahr to its confluence with Arvand Rud river. The Karun is the only navigable river in Iran. And considering its branches, it is its biggest river. An iron suspension bridge, mainly used for cars, spans this river