Also known as The Great Mosque of Ez-Zitouna, Ez-Zitouna or Ezzitouna Mosque.

The mosque of Al-Zaytuna is of the same type as those of Cordoba and Kairouan; an extensive courtyard leading to a stone hall with a roof supported by wooden beams. The roof extends on a surface of 1344 m2. About 160 antique columns and capitals divide the mosque into 15 naves and 6 bays. It is clear that the antique material originates from the ruins of Carthage.

The square minaret stands from the north-western corner of the courtyard. Built in 1894, it is 43 m tall and imitates the decoration of the Almohad minaret of the Kasbah mosque with its limestone bracelet on an ochre sandstone background. Twelve doors open onto the souks. Two are noteworthy: the door of the imam, on the qibla wall, framed with a Roman lintel and sculpted marble pillars; and a western door with a date inscription. The façade has a courtyard with colonnades and Hafsid capitals.

The centre nave and the transverse nave of the transept are larger than the others (4.80 m instead of 3 m). They intersect at right angles to a mihrab, forming a T-shape. The mihrab is equipped with a fluted cupola and an octagonal drum with a square base. It has an inscription attributed to the Abbasid caliph al-Mustin.

A round gallery was added to the trapezoid court in the AH 4th / AD 10th century. Consequently, the narthex has masked the kufic inscription of the AH 3rd / AD 9th century that is still on the façade behind the gallery. The entry dome is heavily ornamented, with alternating rows of ochre stone and red brick. The profusion of niches covering the square base and the octagonal drum is characteristic of the Fatimid style.

Al-Zaytuna building was a major defence station facing the sea. Two control towers on the north-eastern and south-eastern corners remain intact.