of Muhammad and 'Ali. The grille is formed of a radiating six-pointed star with a lamp hanging in the center. One scholarly claim argues that this window represents a mihrab (prayer niche), similar to a flat stucco mihrab found in the Mosque of Ibn Tulun; however, the mihrab referred to has a star hanging from a chain and not a lamp. A more plausible argument proposed by another scholar is that the window represents a shubbāk, the grille from which the caliph appeared to the public on Fatimid ceremonial occasions, specifically symbolizing a famous grille taken by the Fatimids from the palace of their Abbasid rivals in Baghdad and placed as an emblem of victory in the neighboring palace. Near the grilled window, on the same side of the façade, are carved panels representing doors. One possible interpretation of the doors is in reference to the famous Shi'i hadith: "I am the city of knowledge and 'Ali is its gate". The carved panels could also have a political interpretation rather than a religious one, representing the doors of the caliph's court (Bab al-Majlis) in connection with the official role of the mosque's founder, al-Ma'mun al-Bata'ihi, as master of the door (Sahib al-Bab); thereby symbolizing the Fatimid vizier's function in governing who had access to the caliph. Although the grilled window and the carved door panels represent real objects, their particular use as part of the façade's decorative scheme grants them a metaphorical meaning associated with the historical framework of Fatimid caliphal rituals. Between the carved image of the window and of the doors there was once a decorative roundel or medallion which was later cut out and removed at some later unknown date, leaving the brickwork of the wall exposed. The 1990s restoration filled in this empty space with a rosette, hiding the brickwork once again. Scholars Doris Behrens-Abouseif has suggested that the original roundel was removed because it conveyed a message or concept that was later deemed unorthodox, or because it because it contained an inscription glorifying al-Ma'mun which the caliph resented after the vizier's arrest. Lastly, the main foundation inscription of the mosque runs along the top of the façade, directly below the cornice of the building. Much of the inscription is missing, but what still survives mentions the reigning caliph al-Amir, his father al-Musta'li, and the vizier al-Bata'ihi. It translates as follows:(Basmala, has ordered its construction ...