mountain range forming a natural frontier between Pakistan and Afghanistan, extending westward for 100 miles (160 km) from the Vale of Peshāwar (Pakistan) to the Lowrah Valley (Afghanistan). The boundary between the two countries runs along the summit of the range, which reaches a height of 15,600 feet (4,760 m) in the west at the point where the boundary turns southward. The range forms an almost unbroken 14,000-foot (4,300-metre) wall that towers above the surrounding hills. It separates the basin of the Kābul River (north, chiefly in Afghanistan) from the Kurram and Afridi Tīrāh regions (south, largely in Pakistan). Except for a narrow trough cut by the Kābul River, which breaks through the mountains to flow eastward into the Indus River, the range connects directly with the Shandūr offshoot of the Hindu Kush mountain system. The strategic and historic Khyber Pass (q.v.) lies in the eastern part of the mountains. The northern spurs of the range are extremely barren, but the intervening valleys support agriculture and gardens abounding in mulberries, pomegranates, and other fruits. The main range and the upper portions of the spurs are wooded with pine and deodar.