Flysch de Zumaia Nature · Zumaia, Urola Kosta, Gipuzkoa Geological formation visible on Itzurun beach, made up of rock strata that continuously document some 60 million years, including the Cretaceous-Paleogene boundary; it is a global geological reference point for the Paleocene. Photo: Simoncio (CC BY-SA 4.0) What to see and do in Zumaia