Khyber Pass, the largest and the most renowned of these, is 56 kilometres long and connects Kabul in Afghanistan with the fertile vale of Peshawar in the NWFP. The Tochi Pass connects Ghazni is Afghanistan with Bannu in Pakistan and the Gomal Pass provides a route from Afghanistan to Dera Ismail Khan which overlooks the Punjab Plain. the Bolan Pass connects the Sindh Plain with Quetta in Balochistan and onward through Chaman with Afghanistan. Enclosed by the brnahces of western mountains are a number of fertile plains which have been formed by rivers rising from these mountains and falling into Indus. From north to south are the vale of Peshawar (Kabul River), Kohat Plain(Kohat River) and Bannu Plain (River Kurram and Tochi), Peshawar valley covers some 2,200 sq. miles (5,698 sq.km) and is very fertile. It is irrigated by a network of canals which are supplemented by water of the Warsak Dam on Kabul River. Wheat, maize, sugarcane tobacco and sugarbeet are cultivated in large quantities. Large industrial Plants have been established at Peshawar, Mardan, Nowshera and Charsadda. The sugar mills at Mardan and Charsadda are reported to be the largest in Asia. Kohat valley is uneven and broken, but has fertile soil. The Tanda Dam on River Kohat supplemented water of the tubewells and the small tanks formed by damming the rivers. Wheat, barley, gram, maize, rice and melons are grown in substantial quantities. Kohat (76,000), an important town, owes its significance as a marketing centre and a cantonment. The Bannu lowland is made of sandy and gravelly materials brought down by rivers, except for a small area near Bannu town (43,000), which contains rich silt. Perenial irrigation, made possible by the construction of the Kurram Garhi Dam on River Tochi, is confined to the land between River Kurram and River Tochi. The Bannu plain produces wheat, gram, maize, barely, rice and sugarcane. In unirrigated parts of Kohat and Bannu plains are raised flat tailed sheep,camels and donkeys and wool is the most important commerical crop.