 The Cordillera Central and Cordillera Septentrional are separated by the lowlands of the Cibao Valley and the Atlantic coastal plains, which extend westward into Haiti as the Plaine du Nord (Northern Plain).The lowest of the ranges is the Cordillera Oriental, in the eastern part of the country.The Sierra de Neiba rises in the southwest of the Dominican Republic, and continues northwest into Haiti, parallel to the Cordillera Central, as the Montagnes Noires, Chaîne des Matheux and the Montagnes du Trou d'Eau.