he Great Mosque of Córdoba’s interlocking arches, soaring domes, and brilliantly colored mosaics are an enduring symbol of the cultural and architectural influence of the Umayyad Caliphate in al-Andalus (A.D. 756–1031) on the city—but the history of some of these decorations has remained opaque. The emir ‘Abd al-Rahman I (reigned A.D. 756–788) began building the mosque,, an enclosed space reserved for the caliph, and the facade and dome of the mihrab, or prayer niche. Expert mosaicists used gold leaf and richly hued green, blue, and red glass cubes, or tesserae, to create floral and geometric motifs and to emblazon verses from the Koran and historical inscriptions on the walls of the mosque’s most sacred spaces. Islamic sources written in the twelfth and fourteenth centuries claim that the colorful tesserae were a gift to the caliph from one of the Byzantine emperors who ruled from Constantinople in the mid-tenth century A.D. But because the mosaics have been restored many times since they were installed, scholars have not been able to confirm these accounts—or even say how much of the glass is original.
