Biscay, Bay of

Biscay, Bay of, vast inlet of the Atlantic Ocean, south-eastern Europe, bounded on the north and east by France and on the south by Spain. The maximum width and length are about 640 km (400 mi). The southern coast is precipitous and rocky. In the south-east between the mouths of the Adour River and Gironde estuary, the coast is low and sandy, with many lagoons. Low marshland prevails for about 320 km (200 mi) north of the Gironde, but beyond the Quiberon Peninsula the coast is moderately elevated and rocky. Numerous streams run into the bay from the mountains of Spain and through the rivers Loire, Charente, Gironde, and Adour in France. The chief ports are Gijón, Santander, Bilbao, and San Sebastián in Spain; and Bayonne, Bordeaux, Rochefort, La Rochelle, Nantes, and Lorient in France. Among the principal islands in the bay are Belle-Île, Noirmoutier, Île de Ré, and Oléron. Navigation is difficult and dangerous because of the prevailing north-western winds and a strong current.