important natural gateway through the Central Brāhui Range in Balochistān province, Pakistan, connecting Sibi with Quetta by road and railway. For centuries it has been a route for traders, invaders, and nomadic tribes between India and higher Asia. It comprises a series of long, narrow valleys or gorges and extends for 55 miles (89 km) from Rindli in the south to Darwāza near Kolpur in the north. Its widest point (16 miles 【26 km】) is in the Laleji Plain south of Mach. The Nāri-Bolān Canal Project provides for the irrigation of about 24,000 acres (9,700 hectares) by means of damming the monsoon flow of the Bolān River in the Sibi Plain.