In the region of Las Merindades, north of the province of Burgos, the largest karst complex in the Iberian Peninsula and one of the ten largest in the world with its almost one hundred kilometers in length of galleries makes its way.

This underground world is of great interest from a morphological, hydrological, scientific, historical and educational point of view, since prehistoric sanctuaries and remains of sixty-three species of cave-dwelling invertebrates have also been found inside, some of which are exclusive to these caves.

Externally, the landscape presents the characteristic easily eroded limestone formations, which results in a capricious scenario in which the Guareña and Trema rivers disappear into sinkholes to continue their sculptural work in the caves and emerge again a few kilometers later.