The period of the Umayyad Emirate and Caliphate in Cordoba, which marked the peak of Muslim power in Al-Andalus, was an especially crucial era which saw the construction of some of the region's most important early Islamic monuments. The Great Mosque of Cordoba is frequently cited by scholars as a major influence on the subsequent architecture of the western regions of the Islamic world due to both its architectural innovations and its symbolic importance as the religious heart of the powerful Cordoban Caliphate. Many of its features, such as the ornamental ribbed domes, the minbar, and the polygonal mihrab chamber, would go on to be recurring models of later elements in the Islamic architecture of the wider region. Likewise, the decorative layout of the "Bab al-Wuzara"' gateway, the original western gate of the mosque, demonstrates many of the standard elements that recur in the gateways and mihrabs of subsequent periods: namely, a horseshoe arch with decorated voussoirs, a rectangular "alfiz" frame, and an inscription band. Georges Marçais (an important 20th-century scholar on this subject) also traces the origins of some later architectural features directly to the complex arches of Al-Hakam II's 10th-century expansion of the mosque, namely the polylobed arches found throughout the region after the 10th century and the "sebka" motif which became ubiquitous in Moroccan architecture after the Almohad period (12th-13th centuries). Moreover, for much of the 10th century the Caliphate of Cordoba held northern Morocco in its sphere of influence. During this period Caliph Abd ar-Rahman III contributed to the architecture of Fez by sponsoring the expansion of the Qarawiyyin Mosque. The same caliph also oversaw the construction of the first minaret of Cordoba's mosque, whose shape – a square-based shaft with a secondary lantern tower above it – some scholars see as precursor to other minarets in Al-Andalus and Morocco. Around the same time, in 756, he also sponsored the construction of a similar (though simpler) minaret for the Qarawiyyin Mosque, while the Umayyad governor of Fez sponsored the construction of a similar minaret for the Mosque of the Andalusians across the river.