ALPHONSO X, El Sabio, or the learned (1252-1284), is perhaps the most interesting, though he was far from being the most capable, of the Spanish kings of the middle ages. (His merits as a writer are dealt with in the article SPAIN: Literature). His scientific fame is based mainly on his encouragement of astronomy. It may be pointed out, however, that the story which represents him as boasting of his ability to make a better world than this is of late authority. If he said so, he was speaking of the Ptolemaic cosmogony as known to him through the Arabs, and his vaunt was a humorous proof of his scientific instinct.
As a ruler he showed legislative capacity, and a very commendable wish to provide his kingdoms with a code of laws and a consistent judicial system. The Fuero Real was undoubtedly his work, and he began the code called the Siete Partidas, which, however, was only promulgated by his great-grandson. Unhappily for himself and for Spain, he lacked the singleness of purpose required by a ruler who would devote himself to organization, and also the combination of firmness with temper needed for dealing with his nobles. His descent from the Hohenstaufen through his mother, a daughter of the emperor Philip, gave him claims to represent the Swabian line. The choice of the German electors, after the death of Conrad IV in 1254, misled him into wild schemes which never took effect but caused immense expense. To obtain money he debased the coinage, and then endeavoured to prevent a rise in prices by an arbitrary tariff. The little trade of his dominions was ruined, and the burghers and peasants were deeply offended. His nobles, whom he tried to cow by sporadic acts of violence, rebelled against him.
His second son, Sancho, enforced his claim to be heir, in preference to the children of Ferdinand de la Cerda, the elder brother who died in Alphonso's life. Son and nobles alike supported the Moors, when he tried to unite the nation in a crusade; and when he allied himself with the rulers of Morocco they denounced him as an enemy of the faith. A reaction in his favour was beginning in his later days, but he died defeated and deserted at Seville, leaving a will by which he endeavoured to exclude Sancho and a heritage of civil war.
In addition to his other achievements, Alphonso X commissioned numerous works during his reign, including the Cantigas de Santa Maria (400+ songs mentioning the Virgin Mary) and the Libros de las Juegos, or book of games.
http://www.pbm.com/~lindahl/cantigas/ Cantigas de Santa Maria (facsimile and more)
http://www.geocities.com/Yosemite/Gorge/3154/ Libros de las Juegos (illustrations and info)
Initial text from 1911 encyclopedia -- Please update as needed