The Massif of Ardines is one of the most important karst systems in all Asturias. This limestone mountain contains in its interior a network of caves formed over thousands of years.

The underground channel of the San Miguel River carves hollows and caves that add to stalactite and stalagmite formations, columns and karst formations to make up a singular landscape that appeals to the curiosity of many visitors.

The major caves of the Massif of Ardines are the Tenis, the tallest cave looking out over the Sella River through a natural viewpoint; the Cuevona, an immense geological dome lit by a spectacular zenithal opening; and the Lloseta that is communicated with Tito Bustillo via a narrow sinkhole that was definitively known to Palaeolithic groups, as evidenced by the marks and representations around it.

And then is Tito Bustillo, an impressive geological and archaeological site. The natural entrance –occupied by prehistoric tribes- takes to a room known as the Crossroads, a meeting point for the corridor from the original entrance, the corridor to the Main Panel and the start of the long tunnel leading down to the end of the cave.