The Great Mosque of Salé has been in continuous use since 1196 — the same Almohad sultan, Yacoub al-Mansour, who started Hassan Tower across the river also founded this mosque the same year, and unlike Hassan, this one was actually finished. It is the third-largest mosque in Morocco, the oldest religious building in Salé, and the gravitational centre of the medina that grew up around it on the right bank of the Bou Regreg.

Non-Muslims cannot enter the prayer hall. The exterior, however — ochre stone walls, the classic square Almohad minaret, the smaller secondary minarets, and the small square in front — is fully visitable and the natural focal point of the Salé medina. Friday around midday is the moment to see the mosque alive: the square in front fills with worshippers, informal vendors set up at the edges, and the weekly procession has the genuine community feel that Rabat's more administrative monuments do not deliver. Ramadan evenings are the second window, when crowds gather for taraweeh prayers.

The religious complex extends beyond the main mosque. The Medersa Abu al-Hassan, a Merinid Qur'anic school built between 1333 and 1341, sits immediately behind the mosque and is visitable for a small ticket. The Zaouia of Sidi Ahmed Ben Achir, an important local saint, lies further inside the medina (exterior only). For a photograph, the small square at the northwest corner gives the minaret rising above the ochre walls with the medina rooftops behind; the Medersa Abu al-Hassan's roof terrace offers a rare higher angle.