Horseback riding in Cantabria, Asturias, or Basque country?

Does anyone have suggestions for places to rent horses to ride, maybe on the beach in Cantabria, or in Picos de Europa? We'll be staying in that area for a few weeks and would love to do that with our family. We'll also be in Biarritz for a while and will spend lots of time in both the Spanish and French Basque countries. Eddie.....Calibasco.....?