I agree with NewHilton. Although my experience in Spain has been limited to crossing a bridge from France, buying a souvenir and crossing back, I teach about the pilgrimage to Santiago de Compostela and have followed many of the French routes that lead there. It has grown enormously in the past twenty years -- you might find it interesting to walk a bit of the route (not the whole thing, especially in summer!). If you do go to Santiago de Compostela, continue on to Finisterre. And if you're near the French border, be sure to visit St-Jean Pied-du-Port, which is amazing.