PR-S73 Macizo de las Enguinzas is characterised by the limestones of the mass of Las Enguinzas, ideal for the karstification associated to water activity on this material. The mass is located in mid Miera valley to the south.

Inside of this mass, the fragile structural lines follow this formation west to east, and we will have the opportunity of recognise here the holes of Castrejón-Fiñumiga-Yugo Ruyo and Juntarnosa-Irías.

In the first stage of the route, going to Hoyo de Castrejón, we can see on the pathway a fault line with dark limestones and sandy rocks on which we can see an irregular pasture near La Cantolla. The path of Guspedroso, known as “Calzada de las peñas”, appears at many stages cobbled, which points to an ancient busy road for wood transportation.

Before reaching Hoyo de Castrejón, we cross an intensely karstificated area. Hoyo de Castrejón appears crossed by the trail that gives access to Pozos de Noja, actually two artificial water reservoirs used once upon a time by Electra Pasiega.

We known return to take a right into the path that will take us to Fiñumiga. Between the beech forest, we can find a rare building dating from 18th century used as ice storage.

Hoyo de Juntarnosa is the next stop, after a landscape of pastures on a limestone setting with cottages and forests made of ash, beech and hazelnut trees.

By crossing Juntarnosa, we get to see the main Miera valley. The return to the starting point is done through paths and trails following the oriental wall of the mass, accessing Irías and crossing the pastures and forests of Hondales.