Stage Bilbao to Castro Urdiales (By bike)

At around 51.3 kilometres, this stage brings together in a single day's ride the two walking stages that separate Bilbao from Castro Urdiales: the urban one to Portugalete and the coastal one that crosses into Cantabria. It is a day of two halves — a first section completely flat along the estuary and a second broken up along the cliffs — which poses no real difficulty in terms of endurance, but does demand attention to traffic at certain points.

The exit from Bilbao does not follow the official walking route, which climbs towards Cruces and strings together several hills inland, but rather the bidegorri that accompanies the left bank of the Nervión. It amounts to some nineteen kilometres of cycle path, practically flat and segregated from traffic, between the former industrial esplanades of Barakaldo and Sestao, today converted into promenades. The section is not remarkable for its scenery, but it is covered quickly and without incident.

Portugalete receives the cyclist beneath the Bizkaia Bridge, the oldest transporter bridge in the world still in service, inaugurated in 1893 and declared a World Heritage Site. It is worth climbing up to the old town, huddled on the slope around the basilica of Santa María and the Salazar tower, before continuing through Santurtzi and Zierbena. The road skirts the outer harbour and comes out at La Arena beach, where the Camino regains the open sea.

At Pobeña begins the Itsaslur path, laid along the bed of the old mining railway that brought ore down to the Campomar loading bay. Access is by a staircase of some one hundred and twenty steps that forces you to shoulder the bicycle; once past it, the surface is comfortable and the route spectacular, hanging above the cliffs as far as Kobarón and, now as the Piquillo greenway, on to Ontón. Anyone preferring to avoid the steps can follow the N-634, faster but with heavy traffic.

Ontón marks the entry into Cantabria and the point where the itinerary forks. The official variant turns inland through Baltezana, the Alto de La Helguera and Otañes, somewhat longer but quiet and well surfaced; the alternative follows the N-634 through Saltacaballo and Mioño, shorter and more direct, though hardly advisable at rush hour. Both converge at Sámano and drop down to Castro Urdiales, the Roman Flaviobriga, arranged around a headland where the Gothic church of Santa María de la Asunción, the castle of Santa Ana — converted into a lighthouse — and the medieval bridge linking them to the chapel of Santa Ana stand together. Below lie the fishing harbour, the terraces along the promenade and Brazomar beach.