The mountains and valleys of the Dominican Republic divide the country into the northern, the central, and the southwestern regions. The northern region, bordering the Atlantic Ocean, consists of the Atlantic coastal plain, the Cordillera Septentrional (or Northern Mountain Range), the Valle del Cibao (Cibao Valley), and the Samaná Peninsula. The Atlantic coastal plain is a narrow strip that extends from the northwestern coast at Monte Cristi to Nagua, northwest of the Samaná Peninsula. The Cordillera Septentrional is south of, and runs parallel to, the coastal plain. Its highest peaks rise to an elevation of over 1,000 meters. The Valle del Cibao lies south of the Cordillera Septentrional. It extends 240 kilometers from the northwest coast to the Bahía de Samaná in the east and ranges in width from 15 to 45 kilometers. To the west of the ridge lies the Valle de Santiago and to the east is the Valle de la Vega Real. The Samaná Peninsula is an eastward extension of the northern region, separated from the Cordillera Septentrional by an area of swampy lowlands. The peninsula is mountainous its highest elevations reach 600 meters.

The central region is dominated by the Cordillera Central (Central Range) it runs eastward from the Haitian border and turns southward at the Valle de Constanza (or Constanza Valley) to end in the Caribbean Sea. This southward branch is known as the Sierra de Ocoa. The Cordillera Central is 2,000 meters high near the Haitian border and reaches a height of 3,087 meters at Pico Duarte, the highest point in the country. An eastern branch of the Cordillera Central extends through the Sierra de Yamasá to the Cordillera Oriental (Eastern Range). The main peaks of these two mountain groups are not higher than 880 meters. The Cordillera Oriental is also known as the Sierra de Seibo.

Another significant feature of the central region is the Caribbean coastal plain, which lies south of the foothills of the Sierra de Yamasá and the Cordillera Oriental. It extends 240 kilometers from the mouth of the Ocoa River to the extreme eastern end of the island. The Caribbean coastal plain is 10 to 40 kilometers wide and consists of a series of limestone terraces that gradually rise to a height of 100 to 120 meters at the northern edge of the coastal plains at the foothills of the Cordillera Oriental. Finally, the central region includes the Valle de San Juan in the western part of the country the valley extends 100 kilometers from the Haitian border to the Bahía de Ocoa.

The southwestern region lies south of the Valle de San Juan. It encompasses the Sierra de Neiba, which extends 100 kilometers from the Haitian border to the Yaque del Sur River. The main peaks are roughly 2,000 meters high, while other peaks range from 1,000 to 1,500 meters. On the eastern side of the Yaque del Sur lies the Sierra de Martín García, which extends twenty-five kilometers from the river to the Llanura de Azua (Plain of Azua).

The Hoya de Enriquillo, a structural basin that lies south of the Sierra de Neiba, is also within the southwestern region. The basin extends ninety-five kilome2c0 meters from the Haitian border to the Bahía de Neiba and twenty kilometers from the Sierra de Neiba to the Sierra de Baoruco. The Sierra de Baoruco extends seventy kilometers from the Haitian border to the Caribbean Sea. Its three major peaks surpass 2,000 meters in height. TheProcurrente de Barahona (Cape of Barahona) extends southward from the Sierra de Baoruco and consists of a series of terraces.

Data as of December 1989