Left Bilbao following the east bank out to Getxo.
The first bit is a pig as the route we travelled in is one way for the last bit, so got caught up with contraflows and horrible 2-3 lane underpasses & tunnels to get to the start.
The road runs parallel to the river, 2 streets in until a roundabout and then follows the riverbank out. At Getxo, take the Cable car across to Portugalete (0.60€/person incl bike), then follow the coast towards Santurtzi and onto N-639 following signs for the ferry, but continue on to Zierbena.
As soon as you get past the Bilbao port area the road gets much quieter and there's a cycle lane or hard shoulder to use. Down the hill to La Arena, with beautiful beach and a few beach cafes for breakfast.
Out of La Arena towards Muskiz, along the cycle path for 2km but then turn right at the sign for Pobeña along the BI-3795.
At Pobeña, right at a little roundabout leads you to a bumpy road, but keep left and stick with it because it becomes a Tarmac path of the camino, passing through Covarón, across the border into Calabria, following the coast to Ontón.
The path cuts in under the A-8 flyover back up the hill and round into Ontón and joins the N-634 briefly before the turn off to Otañes and the windy CA-523 which leads you slowly up several steep climbs before a slightly bumpy gritty decent to meet the CA-250.
Turn right and continue down the main road into Castro-Urdiales. Right at the roundabout following signs to centro urbano and playa until you reach the coast and the cycle path into the old town with beautiful views across the Marina to the Cathedral and lighthouse.
Castro-Urdiales for lunch at Marisquería Alfredo- incredible seafood restaurant with stuffed muscles, clams, scallops and octopus. Local specialities such as calamares cooked with onion and anchovies from nearby Santoña.
Reluctantly follow the main road out of Castro to pick up the N-634 towards Santander (signed Allendelagua). This is my favourite bit of road so far (huh?) with smoooth tarmac, wide cycle-friendly hardshoulder and some good climbs and well-cambered freewheeling.
Follow through Orinón and other really pretty towns to Laredo, great hill down into town, skirt the edge rather than up into the finger and on through Colindres.
A right turn at the roundabout 3-4km out takes you onto the CA-241 towards Santoña and a weird landscape of sea marshes and delta. Cycle past the convent perched on a rock at Montehano and continue to the sign for the CA-141 3km on the left to Argoños. Out of Argoños towards Santander and off to Noja on the right to eat & sleep. Great day!
62miles. Max speed 40mph
Total distance so far 196miles or 313 km!!