Hewn by the Irati in the foothills of the Leyre Sierra, the 5km-long pass situated between Lumbier and Liédena looks like a thin cut in the cliff. There are fine views from various spots from here. The old railway line that crossed the gorge has been transformed into a path. After crossing a first tunnel, you continue for more than 2km above the tumultuous river, as numerous vultures, with a wingspan of over a metre, fly overhead.