- Title Teverga, Yernes y Tameza Asturias Centre
It is a protected natural space due to the existence of a peculiar karstic complex, formed by sinkholes and blind valleys that give it a great hydrogeological interest. It has three large cavities: the Sumidoiro del Fondadal, 156 metres deep, the Vistulaz Cave and the Vegalonga System, which with its 5,900 metres of development represents one of the main underground complexes in the region.
In the passes we can find grasslands with fawns and scrubland, generally heather, gorse, holly, Genista occidentalis, hawthorn and blackthorn.
The Puertos de Marabio are located between the municipalities of Yernes y Tameza, Teverga and Proaza, and are bounded to the east by the Peña Padiella mountain range, to the west by the Sierra de la Granda, to the north by Pico Caldoveiro and to the south by the watershed of the river Santibáñez.