The Arab geographer Muhammad ibn Muhammad al-Idrisi (1100-1165) wrote the Book of Roger, a world geography, for King Roger II of Sicily. His work, marking the end of the classical age of Arab geography, sums up much of its achievement.

Al-Idrisi was born in Ceuta in Morocco, a descendant of the sharifian Hammudid dynasty, which had ruled over Málaga until 1057 and over Ceuta and Tangier until 1084. He studied at Cordova, the center of scholarship in Moslem Spain. In his youth he traveled widely, visiting Asia Minor, North Africa, Spain, France, and probably the English coast. At the invitation of Roger II, Norman king of Sicily, he went, not later than 1144, to live at the latter's court in Palermo. Roger's motives in inviting him may have been partly political. Al-Idrisi, as a descendant of a dynasty ruling in Moslem Spain and North Africa, and having an intimate...