The existing frontier is marked on the north by the Cantabrian Mountains; on the east by the Sierra de la Demanda with its offshoots, and by the Serrania de Cuenca; on the south by the Sierra Morena; and on the west by various minor ranges which link together the three more or less parallel chains of the Sierra de Gredos, Sierra de Guadalupe and Sierra Morena.
The western range, the Cordillera Occidental, a part of the boundary between Bolivia and the northern provinces of Chile, closely follows the coast outline and forms the western rampart of the great Bolivian tableland or alta-planicie, which extends from the Vilcanota knot in Peru, south to the Serrania de Lipez on the Argentine frontier, is 500 m.
At the southern extremity of the great plate to is the transverse Serrania de Lipez, the culminating crest of which stands 16,404 ft.
On the eastern boundary of the republic is the Serrania del Darien, an Andean range, partly in Colombia.
In other parts, as in the Basque country, in Galicia, in the Serrania de Cuenca (between the headwaters of the Tagus and those of the Jiicar), in the Sierra de Albarracin (between the headwaters of the Tagus and those of the Guadalaviar), there are extensive tracts of undulating forest-clad hill country, and almost contiguous to these there are apparently boundless plains, or tracts of level table-land, some almost uninhabitable, and some streaked with irrigation canals and richly cultivatedlike the Rcquena of Valencia.
Farther south the mountains clustered on the east of the table-land (Sierra de Albarracin, Serrania de Cuenca) long rendered direct communication between Valencia and Madrid extremely difficult, and the principal communications with the east and south-east are effected where the southern table-land of La Mancha merges in the hill country which connects the interior of Spain with the Sierra Nevada.
Immediately to the west of the last-named sierra is the gorge of the Guadalhorce, which affords a passage for the railway from Malaga to Cordova; and beyond that gorge, to the west and south-west, the Serrania do Ronda, a mountain group difficult of access, stretches out its sierras in all direc~ions.
On the other hand, those of the east and south are of great value for irrigation, and the Jticar and Segura are employed in floating timber from the Serrania de Cuenca.
Archean rocks are exposed in the north of the Peninsula, particu larly along the great Pyrenean axis, in Galicia, Estremadura, tb Sierra Morena, the Sierra Nevada and Serrania de Ronda.
The Permian is probably represented by some of the red sandstones, conglomerates and shales in the Pyrenees, in the Serrania de Cuenca, and in Andalusia.
There occur also quartz-porphyry (Sierra Morena, Pyrenees, &c), diorite, porphyrite, diabase (well developed in the north of Andalusia, where it plays a great part in the structure of the Sierra Morena), ophite (Pyrenees, Cadiz), serpentine (forming an enormous mass in the Serrania de Ronda), trachyte, liparite, andesite, basalt.
Besides the cattle reared for field-labor and (in the northern provinces) for regular dairy farming, bulls for bull-fighting are specially reared in many parts of the country, particularly in the forests of Navarre, the mountains separating the two Castiles, the Sierra Morena, and the Serrania de Ronda in Granada, and also in separate enclosures on the islands of the Guadalquivir.