The Nature Trails grouped here take advantage of the old layout of the Bajo Aragón railway, a project that was intended to link La Puebla de Híjar (Teruel) and Tortosa (Tarragona). Although the planned route was never completed, the line was in operation for a few decades, but its poor performance, as well as some landslides, finally led to its dismantling. This railway was popularly known as "Val de Zafán", a name that has been extended to the Nature Trail.