Peñas de Aia Natural Park
The fascinating Peñas de Aia mountains dominate the landscape stretching from San Sebastian to the French border. These are the only granite mountains in the Basque Country and the first natural element that arose from the water some 300 million years ago. It's easy to walk along the backbone of the range up and over its three characteristic humps: Irumugarrieta, Txurrumurru and Erroilbide. At the foot of the mountains are the mines of Arditurri, an underground treasure that witnessed intense mining activity in the Iron Age and the Roman era. The interpretation centre, Parketxe de Arditurri, is located in Oiartzun.