Zumaia, Basque Country, Spain. The town has two beaches (Itzurun and Santiago), which are of interest to geologists because they are situated among the longest set of continuous rock strata in the world. Known locally as the "flysch" they date from the mid-cretaceous period to the present, a time period of over 100 million years. The K-T boundary is present at the Itzurun beach, and fossils can be found, notably of ammonites. The strata stretches along a distance of about 8 km.