The Mount Lebanon area is rugged; there is a rise from sea level to a parallel mountain range of about 2,000–3,000 m (6,600– 9,800 ft) in less than 40 km (25 mi), and heavy downpour of winter rains has formed many deep clefts and valleys in the soft rock. The terrain has profoundly affected the country's history in that virtually the whole landscape is a series of superb natural fortresses from which guerrilla activities can render the maintenance of control by a centralized government an intermittent and costly affair. East of the Mount Lebanon Range is the Bekaa Valley, an extremely fertile flatland about 16 km (10 mi) wide and 129 km (80 mi) long from north to south. At the eastern flank of the Bekaa rise the Anti-Lebanon Range and the Hermon extension, in which stands Mount Hermon straddling the border with Syria. Lebanon contains few rivers, and its harbors are mostly shallow and small. Abundant springs, found to a height of 1,500 m (4,900 ft) on the western slopes of the Lebanon Mountains, provide water for cultivation up to this height.