Excerpts from Books and Wikipedia
"The first challenge to the Abbasids' spiritual authority came from the Fatimid rulers of Egypt, who promoted themselves to the rank of caliph in 910. The Fatimids were Shi'ites, however, and were regarded as heretics by the majority Sunni Muslims. Abd ar-Rahman was the first Sunni ruler explicitly to reject the Abbasid caliphs as both political and religious leaders. . . . As the new caliph, Abd ar-Rahman built an extravagant palace complex at Medinat al-Zhara, outside Cordoba, modeled on the former Umayyad palace at Damascus. Under his rule, Muslim power in Spain would reach its peak, although the caliphate would eventually collapse in a civil war that broke out in 1008." [1001 Days]
"In the days of this father and son al-Andalus could boast of four hundred flourishing towns and cities, seventeen colleges and universities, and seventy well-stocked libraries. Cordova alone had six hundred mosques, nine hundred public baths and eighty schools." [Balyuzi: Muhammad and Course of Islam, p. 304]