Continental Spain extends from the Pyrenees, which separate it from France, and from the Bay of Biscay, an arm of the Atlantic Ocean, southward to the Strait of Gibraltar, which separates it from Africa. (Gibraltar itself is a British possession, although Spain has long claimed sovereignty over it.) The eastern and southeastern coast of Spain, from the French border to the Strait of Gibraltar, is washed by the Mediterranean. In the west, Spain borders on the Atlantic Ocean both north and south of its frontier with Portugal. The small republic of Andorra is wedged between France and Spain in the Pyrenees. The five enclaves in Morocco are the only remnants of Spain's former empire. Two of the enclaves, Ceuta and Melilla, are Spanish municipalities and may become provinces. Madrid is the nation's capital and largest city. Administratively, Spain is divided into 50 provinces. However, the division into 17 geographic and historic regions (autonomous regions), generally corresponding to the old Christian and Moorish kingdoms of Spain, has been maintained for most practical purposes. The chief cities, other than Madrid, are Burgos, Valladolid, León, Zamora, and Salamanca in Castile-León; Toledo in Castile-La Mancha; and Badajoz in Extremadura. The center of Spain forms a vast plateau (Span. Meseta Central) extending from the Cantabrian Mts. in the north to the Sierra Morena in the south and from the Portuguese border in the west to the low ranges that separate the plateau from the Mediterranean coast in the east. It is traversed from west to east by mountain chains-notably the Sierra de Guadarrama-and the valleys of the Douro (Duero), the Tagus, and Guadiana rivers. Except for some fertile valleys, the central plateau is arid and thinly populated; wheat growing, viniculture, and sheep raising are the principal rural activities. The plateau comprises Castile-León, Castile-La Mancha, and Madrid, which form the heart of Spain, and Extremadura, which is in the west. To the northeast of the central plateau is the broad valley of the Ebro, which traverses Aragón and flows into the Mediterranean. Aragón has Zaragoza as its chief city; it is historically and geographically connected with Catalonia, which occupies the Mediterranean coast from the French border to the mouth of the Ebro. Barcelona, the chief Catalan city, is the largest port and the second largest city of Spain. The W Pyrenees and the northern coast, paralleled by the Cantabrian Mts., are occupied by Navarre, with the city of Pamplona; the Basque country, with the ports of Bilbao and San Sebastián; Santander; and Asturias, with Oviedo and the port of Gijón. The extreme northwestern section, occupied by Galicia, has a deeply indented coast and the excellent ports of A Coruña, El Ferrol, and Vigo. Along the eastern coast, S of Catalonia, extend the regions of Valencia and Murcia, named after their chief cities. The Balearic Islands, with Palma as their capital, are off the coast of Valencia. The southernmost part of Spain, S of the Sierra Morena, is Andalusia; it is crossed by the fertile Guadalquivir valley. The chief cities of Andalusia are Seville, Córdoba, and Granada, the Mediterranean port of Málaga, and the Atlantic port of Cádiz. The Sierra Nevada, rising from the Mediterranean coast, has the highest peak (Mulhacén, 11,411 ft/3,478 m) in continental Spain. Spanish summers are often very hot, but winters vary sharply, being mild in coastal areas and colder inland.