Cuba's spectacular natural beauty has earned it the name Pearl of the Antilles. The coastline is marked by bays, reefs, keys, and islets. Along the southern coast are long stretches of lowlands and swamps, including the great Zapata Swamp (Ciénaga de Zapata). Slightly more than half the island consists of flat or rolling terrain, and the remainder is hilly or mountainous, with mountains covering about a quarter of its total area. In general, eastern Cuba is dominated by the Sierra Maestra, culminating in Pico Real del Turquino 2,005 m/6,578 ft); around Camagüey are rolling plains and low mountains; central Cuba contains the Trinidad (Escambray) Mountains in addition to flat or rolling land; and the west is dominated by the Sierra de los Órganos. The largest river, the Cauto, flows westward for 249 km (155 mi) north of the Sierra Maestra but is little used for commercial navigation purposes.