Is the name of a mythical place located on the crest of Mount Garate. Its name, literally “peña grande” comes from a large block that forms the natural strata of sandstone in that area. A rock that is attributed to a legend. They are visible on it, traces of footsteps “amabirjinaren oinatzak” left by the Virgin on its way to Itziar. According to legend the Virgin first stepped on this rock, then in the space which houses the shrine of the Virgin of Arritokieta Zumaia and finally in Itziar. This legend refers to the petro glyphs showing this rock. Contains several cups, some natural and others artificial, which have ,well have originated the myth of the traces of the Virgin. The consecrated stone also contains several crosses carved. Certainly Arriaundi is a sacred space from time immemorial. Proof of this is located in the vicinity of the two prehistoric mounds that make Arriaundi megalithic station. All this symbolic and mythic have made Arriaundi stone has for centuries been a benchmark. Thus the stone marks the intersection of two major roads medieval: from Zarautz which goes towards Zumaia and that from Getaria penetrates inside the peninsula. In the meadow next to the stone, pilgrimages were held. These were staged, by way of initiation rites for young men and women in the vicinity.
Todo este valor simbólico y mítico han hecho que la piedra de Arriaundi haya constituido durante siglos un lugar referencial. Así, la piedra marca el cruce de dos importantes calzadas medievales: la que procedente de Zarautz se dirige hacia Zumaia y la que desde Getaria penetra en el interior de la Península. La pradera que se halla junto a la piedra servía en el pasado para la celebración de romerías, protagonizadas, a modo de ritos de iniciación, por jóvenes de ambos sexos de las inmediaciones.