From the mosque, walk east along the seafront rather than taking a taxi. It is twenty minutes or so to the old medina's northern edge, and the walk gives you the one thing photographs of the mosque never do: its scale set against a city that mostly ignores it.
Casablanca's old medina is not Fez or Marrakech, and pretending otherwise leads to disappointment. The town was flattened by the earthquake of 1755, and what stands now is largely nineteenth century — a low tangle of workshops, hardware stalls and cheap clothing that is lived in rather than curated. Give it an hour. Enter near the Sqala, the eighteenth-century sea bastion built into the medina's northern wall, and let yourself get turned around; the quarter is small enough that you will come out somewhere useful.
Lunch is the first real decision of the trip. La Sqala sits inside the bastion itself, a garden courtyard under the ramparts serving tagines, salads and its own bread; it is a calm place to eat in the medina and it fills at weekends. Taverne du Dauphin, a few minutes away towards the port, has been run by the same family since the late 1950s and does the other Casablanca lunch entirely: fried sole, grilled prawns, anchovies, oysters, whatever the boats landed. It is small, it does not shut in the afternoon, and you should expect to pay roughly what a mid-range main course costs anywhere else in the city.
The afternoon belongs to downtown, and it is the part most visitors never register. Between the two world wars Casablanca became a laboratory for French architects who could build things here that planning committees at home would have refused, and the result is a concentration of 1920s and 1930s architecture that the city's heritage campaigners argue is among the most significant anywhere outside Europe. Start at Place Mohammed V, the formal administrative square with its fountain and its considerable pigeon population, and work north through the grid: wrought-iron balconies, zellij tilework grafted onto Deco facades, stairwells worth putting your head into. The Cinéma Rialto, completed in 1929 to a design by Pierre Jabin, is still a working cinema and still has its dome and its mezzanine. The central market dates from the late 1910s and is at its best early, so note it for the following morning if you are passing.
Give the last hour of daylight to the Musée Abderrahman Slaoui, a private collection housed in a 1940s villa a short walk from the grid: Orientalist travel posters, Amazigh silver, gold jewellery and crystal perfume flasks, laid out over three floors of a house that is itself worth the ticket. Entry is around 60 dirhams and it is generally closed at the start of the week, so confirm before walking over. If the architecture is what has hooked you, look up Casamémoire, the heritage association founded in the mid-1990s that has spent three decades arguing for this district; it runs free volunteer-led walks during its annual heritage days.
For dinner, Rick's Café is worth knowing the truth about. It is not a survivor from the film — there was never a real Rick's — but a piano bar and restaurant against the medina wall, opened in 2004 by Kathy Kriger, a former American diplomat, and built to resemble the set. Taken on those terms it is a good evening and a genuinely handsome room. Book ahead.
Start in the Habous quarter, twenty minutes south of the centre by taxi. It was laid out from the 1910s onwards by the Protectorate authorities as a planned new medina — arcaded lanes, keyhole arches and courtyards drawn rather than grown — and the effect is stranger and far more pleasant than that description suggests. This is where Casablancans buy olives, books, djellabas and wedding sweets, and the shopkeepers are markedly less insistent than in the tourist medinas further south.
Anchor the morning on three things. The Mahkama du Pacha, an enormous Hispano-Moorish courthouse and reception palace designed by Auguste Cadet and finished in the early 1950s, has carved cedar ceilings, marble columns and hundreds of rooms; it remains an official building, so access depends on what is happening inside that day, and you should ask rather than assume. The arcades along the quarter's main shopping lane are a good place to buy without haggling for an hour. And Pâtisserie Bennis Habous, a family business since the 1930s working out of a tiled room behind a carved wooden door, is where you buy cornes de gazelle and ghriba by weight. Expect a queue, and expect it to move.
Midday is for one of two indoor stops, depending on the day of the week. The Museum of Moroccan Judaism, out in the Oasis district, is one of very few museums of its kind in the Arab world and covers a community that was central to Casablanca's making: Torah scrolls, silverwork, reconstructed synagogue interiors, ordinary household objects. Its opening pattern follows both the working week and the Jewish calendar, so telephone or check online before crossing the city for it. If it is shut, go instead to the Église Notre-Dame de Lourdes, a 1954 concrete modernist church by Achille Dangleterre whose walls are made almost entirely of stained glass by Gabriel Loire of Chartres — more than 800 square metres of it, telling the story of the Virgin. Entry is free, it is an active parish, and early afternoon is when the colour lands on the floor.
Then head west to Ain Diab and spend the last two hours of daylight on the Corniche. This is the part of Casablanca that behaves like a city on holiday: a long seafront boulevard of cafés, beach clubs and joggers, with the Atlantic doing all the work. Walk it westward towards the mausoleum of Sidi Abderrahmane, a whitewashed zawiya on a rock just offshore. It is a functioning shrine and non-Muslim visitors should not expect to go inside; the approach, the cluster of blue-and-white houses on the rock and the view back along the bay are the reasons to make the walk. Check the state of the tide before committing to the crossing.
For dinner, Le Cabestan is the Corniche's long-standing formal option, a dining room and terrace built into the cliff near the lighthouse with the sea directly below. It is the most expensive meal in this itinerary by a wide margin and it needs booking. The cheaper and more local alternative is simply to eat along the Corniche itself, where grilled-fish places and pizzerias run late and the pavement supplies the entertainment.