The Basque coast between Orio and Getaria is a place where steep green hills fall straight into the Bay of Biscay, and Altxerri is a cave in those hills, a few kilometres from Zarautz, one of the great surf and holiday towns of the province. Zarautz has a long beach, a seafront promenade and over twenty thousand people, which means fuel, lunch and everything else you might need.
The cave is the reason people come. Its walls carry Palaeolithic engravings and paintings of bison, deer, horses and some animals that are hard to identify, made around the end of the last Ice Age, and it was added to the list of Franco-Cantabrian caves recognised by UNESCO. It is not a casual stop. Access is tightly controlled to protect the delicate surfaces, so visits are limited to small guided groups and need booking well in advance, and there may be times when no one goes in at all. Check before you set your route around it. If it is closed, the hills themselves are consolation enough.
On two wheels the area is short and twisty. The coast road between Zarautz and Getaria is a lovely bit of tarmac with views over the sea, but it is narrow and busy in summer, and the villages are full of day-trippers. Inland roads lead up through small farms, apple orchards and pine plantations, with plenty of tight bends and the occasional wet leaf on the surface. Rain here is frequent, so expect damp patches even on bright days, and fog on the ridges in autumn.
Getaria, the birthplace of Juan Sebastián Elcano, who completed Magellan's circumnavigation in 1522, and of the couturier Cristóbal Balenciaga, is worth the detour. It is also the home of txakoli, a young, slightly fizzy white wine poured from a height into the glass, and grilled fish is cooked on the pier. Orio, nearer the cave, is a fishing and rowing town with a quiet river harbour. The Camino de Santiago coastal route passes through both Orio and Zarautz, so you will see pilgrims with scallop shells on the verges. The best time is late spring or September, when the weather is mild and the summer crowds have thinned.