This is a natural arch, the remains of a former cave gallery which has been worn away by erosion, remaining as a relic which bears witness to its existence.
Going up to Gentilzubi, we can see, next to it, the Abrigo de Axlor, currently protected by a metal grille as a result of the continuous thefts it was subject to. This is a cavity in the rock, which is important since it is the oldest archaeological site in Vizcaya, dating from the Musterien period.