The hike begins with the challenging Way of the Cross (Vía Crucis), which leads to the Ermita de la Trinidad. This is the same route traditionally used during the pilgrimage (romería), historically held on the day of the Holy Trinity, the first Sunday after Pentecost. Although the climb is steep, the reward at the ermitage is immediate: a magnificent view stretching across the deep Lumbier gorge, the charming village, and the rolling countryside. The ermita, perched on the edge of the ridge, is the gateway to the most adventurous part of the hike. From the ermita, you continue along the rocky Trinidad ridge (Cresta de la Trinidad). You walk through low scrubland towards the summit. At 845 meters, you reach the geodesic point of the Trinidad, although the summit itself has no specific landmarks. The real attraction here is the wildlife. On the ridge, you can spend hours enjoying the sight of griffon vultures soaring effortlessly overhead or alighting on the jagged rock peaks. Here, you are level with these impressive scavengers. Just past the summit of the Trinidad, a crucial passage follows. The ridge is exited here via a secured descent secured by a chain. Although experienced hikers are generally safe here, this passage is definitely not recommended for those with a serious fear of heights. After this descent, you continue to the Arcos de Lumbier, also known locally as Acantilados de La Piedra. These are two spectacular natural arches, carved into the limestone rock face by thousands of years of erosion. These arches, called "The Elephant's Face" and "The Stone Arch," offer breathtaking windows onto the plain and the gorge below. They are located directly on the cliffs of the Cresta de la Trinidad. After visiting the last arch, you begin the steep, but necessary, descent back to the plateau. Once you reach the bottom, the terrain flattens out, and you'll walk to the most famous section of the trail: the Foz de Lumbier. This impressive gorge, carved by the Irati River, offers an easy, wide path along the route of an old railway line. You'll pass through two short, yet atmospheric, railway tunnels and along wide paths along the water's edge. In the gorge itself, be sure to take the time to observe the griffon vultures. These scavengers nest in the steep, inaccessible rock walls of the gorge. The Foz de Lumbier is their home and the best place to see them up close. Once out of the gorge, follow the path past the visitor center and local dirt roads to complete the loop and return to your starting point.