After being destroyed in 1443 by the Gamboa de Gipuzkoa, it was rebuilt in its present form by 1500. The notable elements of this building are the twin windows on the first floor, the coat of arms and the exterior staircase. This staircase ends in a balcony and although part of the slope was removed in the 17th century, the balcony was kept, the only one of its kind in Bizkaia.
The Aranzibia tower is on a small hill on the banks of the river where the tides come in from the river and the marshes. It was the first convenient point from which to cross the river and from here all the trade in the port of Ondarroa was controlled. This is how the Aranzibia lineage was born, obtaining rents, privileges and public posts.
It is currently private property and can only be visited from the outside.