External to the Meseta Central lie the Pyrenees in the northeast and the Sistema Penibético in the southeast. The Pyrenees, extending from the eastern edge of the Cordillera Cantábrica to the Mediterranean Sea, form a solid barrier and a natural border between Spain and both France and Andorra that, throughout history, has effectively isolated the countries from each other. Passage is easy in the relatively low terrain at the eastern and western extremes of the mountain range; it is here that international railroads and roadways cross the border. In the central section of the Pyrenees, however, passage is difficult. In several places, peaks rise above 3,000 m; the highest, Pico de Aneto, surpasses 3,400 m.
The Sistema Penibético extends northeast from the southern tip of Spain, running parallel to the coast until it merges with the southern extension of the Sistema Ibérico near the Rio Júcar and with the eastern extension of the Sierra Morena. The Sierra Nevada, part of the Sistema Penibético south of Granada, includes the highest mountain on the peninsula and continental Spain, Mulhacén, which rises to 3,479 m. Other peaks in the range also surpass 3,000 m.