The Aiako Harria granite massif came to the surface more than 250 million years ago, in the paleozoic era, surrounded by rocks where they have found fossils of sea animals. At present, the massif dominates a landscape dotted with megalithic monuments and wide forests.
The massif of Pe˝as de Aia or Aiako Harria, shared by Gipuzkoa and Navarre, contains the oldest geological material in the whole Basque Country. Besides explaining its geological evolution, the Natural Park also informs on its inhabitants' prehistory and history, since it preserves outstanding megalithic monuments (cromlechs, mounds and dolmens), as well as the Arditurri mine land, with galleries dating back to Roman times. The Coto Minero de Arditurri has an Interpretation Centre for the Arditurri Mines and Aiako Harria Natural Park, and it also offers different guided tours inside the mine.
The Natural Park, which hides the A˝arbe reservoir that provide to the half of the population of Gipuzkoa (300.000 people) with drinking water, attracts both cycle-tourists, with the Arditurri bidegorri (cycle track), and the mountaineers, with the emblematic ridge formed by the summits of the mountains Hirumugarrieta (810 metres), Txurrumurru (827 metres) and Erroilbide (838 metres, the highest level).
FLORA AND FAUNA
The Bidasoa salmon, which go up the river each year in order to spawn, and the Griffon Vulture are the showiest species in Aiako Harria. Although it also has oak and beech woods, two unusual elements stand out among its flora: the mountain plant Daphne Cneorum and the Soldanella Villosa, which needs well-drained soils.
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