Built in the 17th century to serve the megorashim (Jews descended from those expelled from Spain), this synagogue is trimmed in pretty herringbone green tiles, turquoise octagonal pillars and glowing chandeliers. The guardian can point out the main features, including the original deerskin Torah scrolls in an ark built into the wall, and a mikvah (ritual bath) in the basement, filled by an underground water source. B&W photos of other Jewish sites around Morocco are also on display.
The synagogue, which was renovated in 1999, is still used on high holy days. Derb Djaj is roughly midway along Rue des Mérinides; the synagogue can also be reached via Derb Taquriri, near the cemetery.
For navigation purposes and dealing with local would-be guides: about five minutes' walk due east is a second neighbourhood synagogue from the same period, Al Fassiyine, built by the local Moroccan Jewish community, but it is not regularly open to the public.