On the drive back toward Cangas de Onís, a short detour toward the coast brings you to one of the stranger geological features of the Asturian coastline — the bufones, a series of blowholes in the coastal rock where incoming waves compress air through underground channels and erupt through vents in the cliff top in columns of spray and sound.

The Bufón de Arenillas near Llanes is the most accessible. At high tide with any swell running the effect is dramatic — sudden eruptions of white water from holes in an otherwise flat rock surface, accompanied by a deep percussive boom that you feel before you hear.