Pre-History
Archeologists tell us that Iberia and particularly Southern Iberia was the last home of Neanderthals. The once successful inhabitants of Europe were driven to smaller and smaller habitats, eventually vanishing as a species somewhere near Gibraltar. The direct replacement in Iberia (as everywhere else) was the Modern Human, called Cro-Magnon when speaking of western Europe.
Cro-Magnon left a treasure of sites and relics in Spain. Most stunning of these is the Caves at Altamira (Cuevas de Altamira).
Camino de Santiago
One of the oldest pilgrimages in Europe, this trail begins in southern France and ends at Compostela in Galicia Spain. The legend is (from memory) that the remains of St. James were brought to Compostela in the 9th or 10th century and became a "must see" for Christians of western Europe.
Long story made short, the pilgrims soon found that the enlightenment came with the journey, not the destination (where have I heard this before, Buddha?), and the pilgrimage has gained in popularity through the centuries, becoming the Appalachian Trail of Europe.
There is a Northern Route and a Southern Route, allowing many villages and pueblos to gain from the traditions. Even the Muslims of the Middle ages encouraged and assisted Christians in their Holy Journey.
Today's Pilgrims are called Peregrinos and come from all over the world to walk El Camino de Santiago. There are even 4 and 5 star hotels along the way for those less devout among us, an who distain a night in a farmer's loft. (Pick me, Pick me!!)