Jemaa Bouzafar Mosque, often called the Spanish Mosque, sits on the hillside above Ras el Maa. The mosque itself is rarely used, but the walk up is one of the classic short climbs in Chefchaouen.
Go near sunset for the view back over the blue medina and the Rif mountains. The path is straightforward, though it is exposed enough that midday heat can make it feel longer than it is.