<P> The Cordillera Occidental is separated from the Cordillera Central by the deep rift of the Cauca Valley . The Río Cauca rises within 124 mi (200 km) of the border with Ecuador and flows through some of the best farmland in the country . After the two cordilleras converge, the Cauca Valley becomes a deep gorge all the way to the Caribbean lowlands . </P> <P> The Cordillera Central is the loftiest of the mountain systems . Its crystalline rocks form a towering wall dotted with snow - covered volcanoes that is 500 mi (805 km) long . There are no plateaus in this range and no passes under 10,825 ft (3,299 m). The highest peak in this range, the Nevado del Huila, reaches 17,602 ft (5,365 m) above sea level . The second highest peak is a volcano, Nevado del Ruiz, which erupted violently on November 13, 1985 . Toward its northern end, this cordillera separates into several branches that descend toward the Caribbean coast . </P> <P> Between the Cordillera Central and the Cordillera Oriental flows the Magdalena River . This 1,600 - kilometer (994 mi) - long river rises near a point some 180 km (112 mi) north of the border with Ecuador, where the Cordillera Oriental and the Cordillera Central diverge . Its spacious drainage area is fed by numerous mountain torrents originating high in the snowfields . The Magdalena River is generally navigable from the Caribbean Sea as far as the town of Neiva, deep in the interior, but is interrupted midway by rapids . The valley floor is very deep; nearly 800 km (497 mi) from the river's mouth the elevation is no more than about 300 meters (984 ft). </P> <P> In the Cordillera Oriental at elevations between 2,500 and 2,700 meters (8,202 and 8,858 ft), three large fertile basins and a number of small ones provide suitable areas for settlement and intensive economic production . In the basin of Cundinamarca, where the Spanish found the Chibcha Indians, the European invaders established the town of Santa Fe de Bogotá (present - day Bogotá) at an elevation of 2,650 meters (8,694 ft) above sea level . </P>

Where do the rivers of the northern colombian andes flow