Castile (Kast-eel; Span. Castillo), the central district of Spain, divided by the Castilian Sierras (8730 feet) into Old and New Castile. The former district - so called because it was first recovered from the Arabs - extends north to the Bay of Biscay, is walled in on all other sides by mountain-ranges, and rises to the height of 2500 to 3000 feet in the form of an elevated plateau, mostly trackless, treeless, and dreary. It is now divided into the eight provinces of Palencia, Valladolid, Avila, Segovia, Soria, Burgos, Logrofio, and Santander. The plateau of New Castile, to the south, is also enclosed by mountains, and though lying 1800 feet lower than Old Castile, presents many similar characteristics of soil and scenery. It embraces the provinces of Madrid, Toledo, Guadalajara, Ciudad Real, and Cuenca. Castilian is the literary language of Spain. Area of Old Castile, 25,280 sq. m.; pop. 1,800,000; area of New Castile, 53,035 sq. m.; pop. 3,500,000; total, 78,315 sq. m., with 5,300,000 inhabitants.