We will wrap up our 3-week driving trip around Spain (starting in Barcelona) with a few days on the northern coast before heading into France. Madrid to Burgos to Bilbao is the direct route. Or we can swing west toward Reinosa and try to see rock-cut churches (along the Ebro River? I can only find a photo of one, in Sainte Marie d e Valverde/Cantabria) and a replica of prehistoric cave art in Santillana del Mar. Then west from Santander area to Bilbao. We only plan to spend 2-3 days in Bilbao/San Sebastian. Trip is in spring.
Question: any info on Rock-cut churches? are they worth seeking out? and how about the cave art? We like going off the beaten path, Just wonder if this sidetrip is really worth it, and how long to plan for it. Thanks!!