Casablanca's most ambitious modern building rises directly out of the Atlantic. The Hassan II Mosque was commissioned by King Hassan II, opened in 1993 after six years of construction, and stands partly cantilevered over the ocean on the western edge of the city. Its 210-metre minaret is among the tallest in the world; the prayer hall holds 25,000 worshippers, with a retractable roof, and the esplanade outside takes another 80,000. Hand-cut zellige, carved cedar and marble fill every surface inside.

The mosque is one of the very few in Morocco that admits non-Muslim visitors. Guided interior tours run several times a day outside prayer times and walk you through the prayer hall, the marble ablution rooms and the hammam level below; tickets are sold at the visitor centre next to the esplanade and the cost (around 140 MAD for adults, less for students) covers the guide. Shoes come off at the entrance. The exterior esplanade is free and open all day — the view from the seafront side, with the minaret rising above breakers, is the city's signature image.

Friday prayer times close the interior to visitors. Outside Fridays, morning light softens the marble inside, late afternoon picks up warmth off the ocean, and either window is better than midday for both photographs and crowd density. Budget forty-five minutes for the exterior and esplanade, or ninety minutes if you take the interior tour. Modest dress covers shoulders and knees throughout; women do not need to cover their hair but a scarf to drape over the shoulders is a courtesy on the way in.