The Picos de Europa
The Picos de Europa massif constitutes a unit located in the most easterly part of the Cantabrian Zone within the Iberian Peninsula. The three massifs of the Picos de Europa are composed almost entirely of limestones which were laid down during the Carboniferous Period of between 290 and 345 million years ago. In the Western Massif approximately 1200 metres of carbonates were deposited with very few impermeable horizons so that most formations are suitable for cave development. The geological history of the Picos de Europa since the beginning of the Carboniferous resulted in a region with large speleological potential and the development of cave systems such as Pozo de Cuetalbo (M2) and Pozo del Llastrale (β3) are intimately related to the geological structure and lithology.