The URDAIBAI area has a large number of architecturally and historically significant buildings and heritage sites, all of which make the area unique and as such contributed to its being declared a Biosphere Reserve. They include typical farmsteads, churches, town halls, mills, rural chapels, cemeteries, bridges, harbours, fountains, etc. The most important in terms of symbolic significance is without doubt the Tree of Gernika and the nearby Assembly Hall. There is not room here to list these sites in full, so what follows should be taken merely as some examples of the most significant among them.