Tabales now likened the poet-emir al-Mu‘tamid (1069-91) to Rome’s Caesar. During his reign, the river Guadalquivir (from al-wadi al-kabir, “the great river”) had a different position than it does today, making it more conducive to trade. The city grew exponentially, from some 185 acres to 740. “We see it in our investigations,” Tabales said. “Each house is the same Islamic house.” Yet al-Mu‘tamid, in an era of political instability but creative efflorescence, made a catastrophic mistake. After the fall of Toledo to the Christians in 1085, he lost his nerve and invited the Almoravids, a Berber dynasty who practiced an...