Praia das Catedrais is on the northwest coast of Spain. The characteristic features of the beach are its natural arches and caves, which can be seen only at low tide. During high tide, the beach appears small, but still suitable for swimming. During low tide the size of its cliffs and sea caves is more apparent, ranging from small cracks on the rock to big caves whose roofs have collapsed due to the erosion of the waves. Source: https://en.wikipedia.org/wiki/As_Catedrais_beach