(the ancient Ara Jovis), a town of Spain, in the province of New Castle, 28 miles S.S.E. of Madrid. It is situated in a fertile and well-watered valley on the left bank of the Tagus, immediately above the junction of that river with the Xarana, in Lat. 40. 1. 54. N. Long. 3. 37. 30. W. It is usually the residence of the Spanish Court from Easter till the end of June, during which time the population is increased from 4000 to about 12,000. The town is built in the Dutch style, with avenues of trees, and has numerous hotels, public gardens, theatres, and other places of amusement. The palace was begun by Philip II. and enlarged and embellished by his successors. The gardens are much admired for their rural beauties, fine shaded walks, fountains, and cascades. During the Peninsular war, this place suffered severely from the French. The treaty of 1772 between France and Spain, by which they pledged themselves to assist each other in opposing the English in America, was concluded here; and here, on the 18th of March 1808, broke out the insurrection which ended in the abdication of Charles IV. in favour of his son Ferdinand.