In the central and highest part of the Outer Sierras of the Pyrenees lies the Sierra de Guara (the most important in the Natural Park).

Wind and water have shaped the landscape we see today, with the erosive action of floodwaters through the limestone rock creating a relief with dramatic, spectacular figures known as karst landscapes with chasms, dolines, caves, upwellings, and rock walls, etc.

Within the unique scenery of Sierra de Guara Natural Park, different spots can be found, such as the karstic formation of Cañón del Mascún, the Pliegues de Sierra Lupera y Chasa, the Combe de Balced, the pinnacle modeling of Huevo de Morrando, and the Sugerencias de la Tamara y el Puntillo, all of which have been recognized as sites of geological interest. They, together, explain the origin, formation, and evolution of this valley, as well as the materials that compose it and its structure.