Two dissimilar mountain systems, flanking a central plain, occupy the greater part of the island. The Troodos Massif, in the southwest, attaining its highest point in Mt. Olympus (1,953 m/6,406 ft), sends out numerous spurs to the northwestern, northern, and southern coasts. In the north, a geologically older range, the Kyrenia Mountains, extend more than 160 km (100 mi) along the coast in a series of rocky peaks, capped often by medieval castles. Between these principal formations lies the Mesaoria, a low plain extending from Famagusta Bay on the east to Morphou Bay on the west. Once forested, this now treeless region, varying in width from 16 to 32 km (10–20 mi), contains the bulk of the island's cultivable and pastoral area. There are few lakes or rivers; rivers are little more than rocky channels that carry away torrents during the thaw of spring and early summer.