Caves of Andina Nature · El Franco, Eo-Navia, Asturias Image of El Franco, not of the place itself. The Cuevas de Andina are a system of caves of karstic origin located near the village of Andina, in the concejo of El Franco. The protected area covers 11.90 hectares of a valley formed by a karstic depression, whose rocks, made up of Lower Cambrian marbles from the Vegadeo formation, are a geological rarity in a concejo dominated by slate and quartzite. The depression is barely noticeable under the valley's abundant vegetation, among which yews, hollies, hazels and ash trees stand out. Declared a natural monument in 2002, the system is at an advanced stage of restoration for tourist access, and is the main natural attraction in the interior of El Franco. Photo: Gandalín del Revellón (CC BY-SA 3.0) What to see and do in El Franco