By the time 'Abd al-Rahman reached Spain (in 755 C.E.), the Arabs from North Africa were already entrenched on the Iberian Peninsula and had begun to write one of the most glorious chapters in Islamic history. They also improved trade and agriculture, patronized the arts, made valuable contributions to science, and established Cordoba as the most sophisticated city in Europe.
By the tenth century, Cordoba could boast of a population of some 500,000. The city had 700 mosques and 70 libraries - one reportedly housing 500,000 manuscripts and employing a staff of researchers, illuminators, and book binders. Cordoba also had some 900 public baths, Europe's first street lights.