Legzira is a wide flat beach under rust-orange cliffs, with a sea arch about 27 metres across standing on the sand. Walk under it at low water and the people ahead of you turn into specks. The cliff gets its colour from hematite, an iron oxide cementing the quartz grains together. The rock itself is a mixture of pelite, sandstone and pebbly conglomerate laid down in the Lower Cretaceous, when rivers built a delta here and a rising sea drowned it. There used to be two arches. On 23 September 2016 the other one cracked apart and fell into the surf, after a block dropped away and a fracture opened across its southern face. A heavy autumn swell finished what the Atlantic had been doing to the cliff for centuries.
The tide sets the timetable. At low water the sand opens all the way through the arch and you can wade the shallow film underneath it, camels folded on the dry sand behind you. At high water the ocean is back at the foot of the rock and the passage is gone. Nobody comes here to swim: the shore break is heavy, the currents pull, and the water is genuinely cold. Surfers do come, for the northwest groundswell that arrives from October to March. The last hour of daylight is when the wall burns and the wet sand carries the whole thing upside down. The beach runs about 10 kilometres north of Sidi Ifni, and there are terraces above the tideline to sit on over mint tea and bread. Erosion has not stopped: the arch you photograph today is on the same schedule as the one that fell.