Cuevona of Avín Curiosity · Onís, Oriente, Asturias Image of Onís, not of the place itself. A cavity of some five hundred metres run through by the River Chicu and fitted out to explain the last glaciation in the Picos de Europa; it holds the almost complete skeleton of a young Quaternary rhinoceros. Photo: Nicolás Boullosa from Fontainebleau, France (CC BY 2.0) What to see and do in Onís