From these figures it is easy to perceive how very different is the aspect of these buttress chains when seen from the plateau, and when looked at from the plain from which they rise. Thus the Sierra de Moncayo, 7700 feet, stands out with boldness from the Valley of the Ebro, but viewed from the plateau of Castile it is scarcely noticeable. From its summit, however, the finest view of the whole range of the Pyrenees to be found anywhere on the Spanish side of the chain, is to be obtained. Turning thence towards the south and south-east, these mountain chains--under the various names of the Sierras de Cuenca, de Molina, and Albarracin--divide the river basins of the Mediterranean from the far larger ones of the Atlantic. They have their culminating point in the Muela de San Juan and the Cerro de San Felipe, nearly 6000 feet, at the junction of the three provinces of Teruel, Cuenca, and Guadalaxara. From the sides of these mountains the waters fall with rapid course, on the north to join the Ebro, on the east and south to the Mediterranean; while with gentler slope, but in far greater volume, the Douro, the Tagus, and the Guadiana roll their waters to the Atlantic. From these Sierras the plateau tilts gradually westward and southward, but is intersected by mountain chains, peaks of which towards the west attain a higher elevation than those which form the real culmination of this part of the peninsula. The bare and bleak granite range of the Guadarrama, which divides the basin of the Douro from that of the Tagus, and from whose summits steals the icy wind so fatal to Madrid, attains in its highest summit, Pena Lara, 7800 feet, near Segovia; while in its western prolongation, the Sierras de Credos and de Gata, the Plaza del Moro reaches 8700 feet. The chains which divide the valley of the Tagus from that of the Guadiana are not nearly so well marked as are those more to the north, and rise to a much less elevation above the plateau. Beginning with a south-westerly prolongation of the Cerro de San Felipe, under the successive titles of Montes de Toledo, Sierras de Guadaloupe, Montanchez, and San Mamed, about 2000 feet, they reach the Portuguese frontier near Portalegre. The highest point seems to be in the mountains of Toledo at Villuercas, where a height of a little over 5000 feet is attained. The mountains which separate the basins of the Guadiana and the Guadalquiver, under the names of the Sierras de Alcaroz, Morena, de Cordova, Guadacanal, and Aroche, and which form the southern buttress of the central plateau, present a still greater difference than those of the northern buttress when viewed from the plateau and from the plains of Andalusia. From the former they appear only rolling undulations, and the traveller scarcely notices the rise till he finds himself descending one of the steep and savage gorges, like that of the Pass of Despena-Perroz, on the road and rail between La Mancha and Andalusia.