not tried this one yet

nice training ride, not a lot of cars

Nice quite ride not too many cars, nice views

Ridden or driven all of this route, roads are good, amazing descents solid climbs, some of the best views in the area.

good roads, some nice descents, not to much traffic.

The BI-3104 is a very nice road I did not manage to find the connection with the BI-631 2 roads are indicated on Google but  1 is not road bike compatible, this is important as the Bermeo road is not a nice ride (too much fast traffic). The coast road is as always very pleasant. Bermeo harbor is a nice place for a coffee

Preparacion a la Bilbao-Bilbao 2011