The Portuguese Cistern is El Jadida's most atmospheric interior, a vaulted chamber inside the old fortified city of Mazagan. Built by the Portuguese in the 16th century and later used as a water cistern, it is famous for the thin layer of water that can turn the floor into a mirror.
When the light is right, the columns and ribs seem to float upside down, which explains why photographers and film crews love the place. Access has changed during restoration and safety work, so ask locally before counting on an interior visit; even when closed, it remains the landmark everyone in the old city points to.