What is a horseshoe or keyhole arch in Moroccan architecture?

The horseshoe arch is the shape that makes a building look unmistakably Moroccan, and once you can name it you will see it a hundred times a day. Where a Roman or Gothic arch is a half-circle or a point, the horseshoe arch carries its curve more than halfway round, so the opening pinches in again near the bottom — exactly the silhouette of a horseshoe, or, when it is more angular, a keyhole. That extra sweep gives the arch its graceful, slightly enclosing feel, and it is the calling card of Moorish architecture from Marrakech to the Alhambra in Spain.

You meet horseshoe arches everywhere in Morocco: framing the great gateways of the imperial cities, marching in rows around courtyard arcades, crowning the niches inside mosques and madrasas, and outlining the doorways of riads and palaces. In Fes, the Bou Inania and Al-Attarine madrasas have exquisite examples, often layered with carved plaster and tilework around the arch's edge. Many are 'polylobed' or 'foiled' too — the inner edge scalloped into a run of small lobes — which turns a simple opening into a piece of lace frozen in stone or cedar. I love watching guests instinctively slow down and look up the moment they pass under one.

The arch matters because it carries weight, in both senses. Structurally, the horseshoe form distributes load gracefully and lets builders span wide courtyards with slender columns. Symbolically, it became the architectural signature of Islamic Spain and Morocco — the Umayyads refined it at the Great Mosque of Córdoba, and Moroccan dynasties carried it forward — so to stand under one is to stand inside a thousand years of shared Andalusian-Moroccan heritage. The shape frames a view deliberately, drawing your eye from a shaded arcade out into a sunlit courtyard, and that staging of light and space is the whole point.

A practical tip for travellers: use the arches to read a building's age and ambition. The grandest monuments crown their horseshoe arches with bands of carved gebs (plaster), zellige, and Arabic calligraphy, so the more elaborate the frame, the more important the doorway it announces — often the qibla wall or the main entrance. In humbler homes the same arch appears plain, just the pure curve, and it is honestly just as lovely. Photographers should shoot them from straight on to catch the symmetry, and from the shade looking out, when the bright courtyard beyond turns the arch into a perfect frame.