I visited this WHS in April 2018. Just as Essaouira was formerly known as Mogador, El Jadida was known as Mazagan. Both fortified towns are along the Atlantic coast and both have their own charm even though El Jadida is definitely smaller and lacks the medina atmosphere.

Apart from wandering in the few streets with bilingual names and alphabets in Portuguese and Arabic, the only three things to do here are walking on the fortified walls with a very picturesque view (photo - best time is in the morning), visiting the underground cistern and visiting the Manueline Church of the Assumption.

El Jadida in a way is quite similar to the Three Cities or Mdina in Malta and the Cittadella in Victoria/Rabat, Gozo. Next to the entrance gate is a tower-like monument with the UNESCO WHS inscription plaque. As a little trivia, the UNESCO symbol on the plaque is upside down!

All in all El Jadida is a worthwhile half day trip from Rabat and you can easily stop half way to take in Casablanca too. La Capitainerie is a hidden gem of a restaurant within a former church/chapel and their hummus, calamari dish and/or seafood tajine alone are worth the visit!