by a small water channel across the floor just inside it. The channel allowed worshipers entering the mosque to wash their feet on the way in, and helped with initial ablutions. Next to the mosque is a tower known as the Borj Neffara (, "Tower of the Trumpeters"), an observation tower that is sometimes confused as a minaret but was actually part of another Dar al-Muwaqqit. Prayer hall The interior hypostyle prayer hall takes up most of the mosque's area. Like the interior of most traditional mosques in Moroccan architecture, it is a relatively austere space with mostly plain walls, wooden roofs, and rows upon rows of arches. The main area, south of the courtyard, is a vast space divided into ten transverse aisles by rows of arches running parallel to the southern wall. The southern wall of this hall also marks the qibla. The central axis of the prayer hall, perpendicular to the qibla wall, is marked by a central nave running between two extra lines of arches along this axis, perpendicular to the other arches. This nave leads towards the mihrab: a niche in the qibla wall which symbolizes the direction of prayer, and in front of which the imam usually leads prayers and delivers sermons. This overall layout (a hypostyle hall with a central nave emphasized against the others) is a familiar layout for North African mosques generally. The mihrab, which dates from the Almoravid (12th-century) expansion, is decorated with carved and painted stucco, as well as several windows of coloured glass. The mihrab niche itself is a small alcove which is covered by a small dome of muqarnas (stalactite or honeycomb-like sculpting). On each side of the mihrab's opening is a pair of engaged marble columns topped by deeply-carved capitals. These capitals are spolia from al-Andalus, dating from the time of the Caliphate of Córdoba, which were re-appropriated by the Almoravids for Ali Ibn Yusuf's expansion of the mosque. On the mihrab's façade, the stucco ornamentation of the lower parts, immediately around the arch itself, was most likely redone in the 16th and/or early 19th centuries. The stucco decoration of the upper wall above this still dates from the Almoravid period. The Almoravid decoration prioritizes floral motifs, which contain more diversity than the later restorations below, over which bands of Kufic inscriptions have also been carved. The central nave that runs along the axis of the