This route follows the range of Caballar, signaled as PR S-54.

We will find here different types of rock that stem from the tectonic incident that 35 million years ago formed our “Cordillera Cantábrica”.

We should note other attractions of this setting, like the transition from pastures and cottages to forests of fast-growth species. Also, the mountain range of Caballar, formed by eight Mounts of Public Use, those in the municipality of Villafufre (Caballar, Cuesta mijares, Caballar y Castillo, Caballar y Plantío del Rey) and those in Santa María de Cayón (Alto y Cagigal, Las Podas, Caballar y Juyo or Caballar y Callejo).

One of the best attractions on route is the generous panoramic above the Llerana and Pisueña headwaters. We can also see from here San Martín, Sandoñana, Penilla, Susvilla, Ojuriego, Trasvilla and Rasillo, plus Pisueña and Pas rivers. Standing out is the lineal form of the town of San Martín, resulting from a historical construction linked to the path between both valleys.

We can also see the distribution of the different trees, some looking for humid settings on the riverside and other growing directly on the pastures. Traditional wood usage is preserved.

The walk starts in San Martín in the direction of Sandoñana, and we take the first left turn to ascend between chestnut and oak trees. Further up the mountain is filled with pines and then eucalyptus. It is an easy, short route that offers beautiful views. We descend towards Pas river, quickly losing altitude, to the turn east and follow a trail again to San Martín.