Zumaia and the Flysch.

Zumaia is another of the essential towns on the Basque coast, but it also has an almost unique feature in the world. It has a Flysch, which are rock exposures of sedimentary origin that alternate different layers, and which may sound boring like that, but in Zumaia you can read the layers of hundreds of millions of years of earth history like in a book and it is the third best place in the world to see the K/Pg Limit, the Cretaceous-Tertiary limit, or the moment when the dinosaurs disappeared from the earth.