Hidden among the mountains between Troumouse and Gavarnie is the Cirque d’Estaubé, the most wild and remote of the area's three mountain amphitheatres and only accessible on foot. The trail starts from the turn-off to the barrage des Gloriettes, which you pass on the D922 en route to Troumouse. It’s about a 3½-hour return walk; you'll need proper boots, water and snacks.