Along the headland's cliffs, in sea caves with entrances hidden below the waterline, lives the largest surviving colony of the Mediterranean monk seal, one of the rarest marine mammals on Earth. Cabo Blanco and the Greek island of Gyaros are the only two places in the world where these animals still gather in a true colony rather than scattered, lonely individuals. The species once ranged from the Black Sea across the Mediterranean and out into the Atlantic, hauled out on beaches from Madeira to the Azores. Hunting and disturbance erased them almost everywhere. Here, on a coast too remote and too forbidding for resorts, a few hundred held on.

In the summer of 1997, disaster nearly finished them. A bloom of toxic algae swept the colony, and within weeks roughly two-thirds of the animals were dead, the population crashing from some 350 to little more than 100. It looked like the beginning of the end. Instead, it became the start of a recovery few dared to hope for. Under protection from Mauritania, Morocco, Spain, and Portugal, the colony clawed its way back, and the population has since more than tripled to around 360 animals, with yearly pup births climbing from 26 to roughly 80. The threat of another mass die-off has never gone away. But for now, against long odds, the seals of Cap Blanc are winning.

The headland is divided. On the eastern shore, barely a mile from the line, stands the bustling Mauritanian city of Nouadhibou. On the western shore lies La Guera, a ghost town of empty buildings whose ownership belongs, on paper, to the unresolved dispute over Western Sahara. The boundary was drawn by France and Spain at a convention in 1900, splitting the cape between their colonies; today it separates Mauritania from a territory claimed by Morocco and by the Polisario Front alike. Neither force occupies the western tip, so Mauritania quietly polices it. The arrangement is one of those frozen compromises that hold precisely because no one tests them, a quiet edge of an old quarrel.

Cap Blanc is not the westernmost point of Africa, yet because of the tilt of the Earth it claims a stranger distinction: at least twice a year, it is the last place on the entire continent to see the sun set. A lighthouse has marked the cape since 1910, sweeping the same waters that wrecked countless ships over the centuries. The wider headland is an Important Bird Area, a wintering ground for turnstones, gulls, and Caspian and Sandwich terns. The literature of shipwreck haunts this coast: Captain James Riley beached his vessel near here and survived to write of it, and Herman Melville name-checks Cape Blanco in Moby-Dick. Few places hold so much loss and so much stubborn survival on one strip of sand.