Hindu Kush, great mountain system of Central Asia. Broadly defined, it is some 500 miles (800 km) long and as much as 150 miles (240 km) wide. The Hindu Kush is one of the great watersheds of Central Asia, forming part of the vast Alpine zone that stretches across Eurasia from east to west. It runs northeast to southwest and divides the valley of the Amu Darya (the ancient Oxus River) to the north from the Indus River valley to the south. To the east the Hindu Kush buttresses the Pamir range near the point where the borders of China,