The route reaches the diversion of the Boj ravine and turns to the left along the path that follows the shore of the small mountain stream, marked with the blue color of a Nordic walking itinerary. The water of the stream is part of the drainage of the Ibón de Piedrafita and the flow of the Cuasta ravine, in the thaw season it forms beautiful jumps on the steps of the land and it is a delight to listen to the stream rising towards the glacial cirque where the lagoon is. The Peña Telera and Peña Blanca crests emerge in front of the road like a stone border at the end of the world, they seem unattainable cut by dizzying abysses and inaccessible walls.
The path leaves the Boj ravine and reaches the shore of the Ibón de Piedrafita, the lacustrine treasure of Peña Telera, submerged in a panoramic glacial cirque with excellent views of the mountains and valleys of the Tena Valley. The little lake has an artificial wall to increase the reservoir level but it does not detract from the attractiveness or environmental quality of this wonder of the Pyrenean lakes. Mountaineers and collectors of great peaks have at hand the ascent of Peña Telera by the steep path of the Cabachirazas pass, connecting later with a quite vertiginous crossing, and in winter very exposed and dangerous, up to the Neck of Telera and the summit of this emblematic mountain of the Tena Valley.