Perhaps my readers can illuminate me about this. I spotted variations on this type of construction on numerous small farms located along the Camino. Some appear quite old. I first thought it might be used for storing corn. But now I'm not so sure. Do you know what it is?
Thanks to all who responded. Your comments finally led me to this Wikipedia article:
"An hórreo is a typical granary from the northwest of the Iberian Peninsula (mainly Galicia, where it might be called a Galician granary, Asturias and Northern Portugal), built in wood or stone, raised from the ground by pillars (pegollos in Asturian, esteos in Galician, abearriak in Basque) ending in flat staddle stones (vira-ratos in Galician, mueles or tornarratos in Asturian, or zubiluzea in Basque) to prevent access by rodents. Ventilation is allowed by the slits in its walls."