Right after a barrier, reach an intersection under a large oak tree (90m): be careful to choose the path that goes up to the right. At the top of the climb, go through a gate and then walk on the forest path on the edge of the fence. It then descends through several valleys and undergrowth. After a stream, the path starts to go up into the forest. At the Y-shaped intersection, ignore a track on the left and continue to climb on the right under the oak and chestnut trees. Right after passing under the high voltage line, find the path you took earlier, which you can take down to the left to return to Biriatou.