Keel arch

The keel arch is a pointed arch shaped like an upturned boat; Yeomans counts it a Fatimid innovation that replaced the round arches of the first al-Azhar mosque and remained, structural or decorative, a distinctive feature of Cairene architecture until the Ottoman conquest. ^{1 2}

In the qibla-arcade dome of al-Azhar, from the reign of al-Hafiz, the dome rests on keel arches over antique columns braced by wooden tie-beams; Yeomans sees these features as defining Fatimid structure, much lighter than the solid brick piers of Tulunid building. ¹ The keel arch also became a decorative frame: the façade of al-Aqmar (1125) has three keel-arched niches with fluted hoods, and its arcades are keel arches on antique columns framed by Kufic bands. ^{3 4} The portico of the mosque of al-Salih Tala'i (1160) has five keel arches on Corinthian columns, and its arcades are keel arches outlined in Kufic. ^{5 6}

Keel-arched panels decorate the first storey of the minarets of Qaytbay and al-Ghuri at al-Azhar, from the late Mamluk period, and the northern minaret of the mosque of al-Hakim completed by Baybars al-Jashankir. ^{7 3}