Al-Mahdi

Born in 744 or 745 as Abū ʿAbd Allāh Muḥammad ibn ʿAbd Allāh al-Manṣūr, he took the regnal name al-Mahdī—"He who is guided by God"—when he succeeded his father, al-Mansur, as caliph in 775. The ten years that followed turned him into an architect of sacred space. He expanded the Prophet's Mosque in Medina, reconstructed the Al-Aqsa Mosque in Jerusalem with fifteen aisles and a central dome—larger than the current seven-aisle Fatimid layout—and oversaw the expansion of Mecca's Masjid Al-Haram on a scale unmatched until the Saudis began building in the modern era. He died in 785.