The southern portion of the Meseta () is further divided by twin mountain ranges, the Montes de Toledo running to the east with the Sierra de Guadalupe, to the west. Their peaks do not rise much higher than 1,500 m. With many easy passes, including those that connect the Meseta with the Andalusian Plain, the Montes de Toledo and the Sierra de Guadalupe do not present an obstacle to transportation and communication. The two mountain ranges are separated from the Sistema Central by the Tagus River. The mountain regions that rim the Meseta Central and are associated with it are the Sierra Morena, the Cordillera Cantábrica, and the Sistema Ibérico. Forming the southern edge of the Meseta Central, the Sierra Morena merges in the east with the southern extension of the Sistema Iberico and reaches westward along the northern edge of the Rio Guadalquivir valley to join the mountains in southern Portugal. The massif of the Sierra Morena extends northward to the Río Guadiana, which separates it from the Sistema Central. Despite their relatively low elevations, seldom surpassing 1,300 m, the mountains of the Sierra Morena are rugged at their southern edge. The Cordillera Cantábrica, a limestone formation, runs parallel to, and close to, the northern coast near the Bay of Biscay. Its highest points are the Picos de Europa, surpassing 2,500 m. The Cordillera Cantábrica extends 182 km and abruptly drops 1,500 m some 30 km from the coast. To the west lie the hills of the northwest region and to the east the Basque mountains that link them to the Pyrenees. The Sistema Ibérico extends from the Cordillera Cantábrica southeastward and, close to the Mediterranean, spreads out from the Río Ebro to the Río Júcar. The barren, rugged slopes of this mountain range cover an area of close to 21,000 square kilometers. The mountains exceed 2,000 m in their northern region and reach a maximum height of over 2,300 m east of the headwaters of the Rio Duero. The extremely steep mountain slopes in this range are often cut by deep, narrow gorges. Lowland regions The major lowland regions are the Andalusian Plain in the southwest, the Ebro Basin in the northeast, and the coastal plains. The Andalusian Plain is essentially a wide river valley through which the Río Guadalquivir flows. The river broadens out along its course, reaching its widest point at the Golfo de Cadiz. The