The Sierra de Neila (Neila Mountain Range) is mainly renowned for its famous lagoon (small lake with a glacial origin), yet this vast territory includes other locations, interesting both for their geological and panoramic aspects. The river Frío valley and the narrow gorge of Las Cerradas, formed by river Neila, present a large and luxuriant variety of fauna and flora. The elevated height, relief and orientation make it the dampest area in the region of Burgos. Located on the limit of the regions of Soria and La Rioja, the green, fresh landscape presents all the characteristics and attractions of a high mountain location.

These tall mountains, located at over 2,000 metres, are part of the Sistema Ibérico mountain range. Among its materials, there are rocks from the Cambric period, dated 570 millions of years ago, making them some of the oldest rocks on the Peninsula.... The area has endured the erosion of the quaternary glaciations, the remains of which are still visible on the different cirques, moraines and lagoons.

The river Frío valley houses an enormous stone pine tree forest accommodating many wild mammals, such as wolves, which usually breed in the most isolated areas of the forest, alongside roe deer, deer and wild boars; these hills also house badgers, weasels, polecats, squirrels, wild cats, beech martens and hedgehogs. Among the birds, there are birds of prey such as short-toed eagles, kestrels, owls and long-eared owls. Over recent years, several couples of herons have overwintered in this mountain range.

Among the pine trees there are also some isolated examples of yew trees, holly trees, beech trees and mountain ashes. At springtime, the Neila mountain range becomes a genuine showcase of mountain flowers that spread out over the grazing lands composed by heather, gorse, heath, fern and broom.