Besides being considered by some the westernmost tip of the Pyrenees (rivalling with the coastal mountain Jaizkibel), it stands out as a distinctive range of rocky prominences and gullies, otherwise uncommon.
The conspicuous formations of Aiako Harria consist of a Paleozoic massif with some of the oldest materials cropping out currently in the Basque Country.
Later orogeny pushed a mass of igneous rocks to the surface, so metamorphosing the superficial Paleozoic materials as it tore its way out of them, which yielded the present day granitic landscape.

The materials held by the mountain enticed the Romans to these reaches, who settled in the riverside town of Oiasso with important port and factory vestiges unveiled recently.
Ore was extracted from the Arditurri mines (IPA: [aɾ'ðituri]), largely silver bearing galena and lead aimed at the elaboration of different metallic instruments, the site standing for one of the most significant ancient mines in Hispania, second to Las Médulas mines in Leon but matching in importance those of Cartagena or Rio Tinto.
As late as the 5th century, the mines were abandoned by Romans, but were exploited in the Middle Ages for iron, so spurring the construction of many foundries around.
The mines kept on running up to 1984, when the exploitation license expired.
Besides being considered by some the westernmost tip of the Pyrenees (rivalling with the coastal mountain Jaizkibel), it stands out as a distinctive range of rocky prominences and gullies, otherwise uncommon. The conspicuous formations of Aiako Harria consist of a Paleozoic massif with some of the oldest materials cropping out currently in the Basque Country. Later orogeny pushed a mass of igneous rocks to the surface, so metamorphosing the superficial Paleozoic materials as it tore its way out of them, which yielded the present day granitic landscape.
The materials held by the mountain enticed the Romans to these reaches, who settled in the riverside town of Oiasso with important port and factory vestiges unveiled recently. Ore was extracted from the Arditurri mines (IPA: [aɾ'ðituri]), largely silver bearing galena and lead aimed at the elaboration of different metallic instruments, the site standing for one of the most significant ancient mines in Hispania, second to Las Médulas mines in Leon but matching in importance those of Cartagena or Rio Tinto. As late as the 5th century, the mines were abandoned by Romans, but were exploited in the Middle Ages for iron, so spurring the construction of many foundries around. The mines kept on running up to 1984, when the exploitation license expired.
Peñas de Aya