If you are hiking in the FrenchPyrenees one of the nicest places to go wild camping is at Lac de Gaube, a beautiful lake a short walk up from Cauterets and a good base for walking the GR10 or crossing over to Spain. The campsite is alongside a gorgeous lake with clear water and good areas for pitching and makes an excellent stop or picnic ground. The walk up to Lac de Gaube from Cauteret is a very pleasant one and just takes a few hours so you can easily do it after lunch if you have flown into the area in the morning (I few into Lourdes and caught the bus to Cauterets and then walked up on the first day).
The walk is a fairly easy 10km or so, but with a bit of a climb of about 600m or so. But because it follows the rivers and valleys it is cool and beautiful.
From Pont d’Espagne carry on up the valley following the markings for the GR10. When you get to the lake, curve around it to the right following signs for the refugue des Oulettes de Gaube. A short walk around the lake to the southern end will get you to a nice flat area that is perfect for pitching tents. The only downside we had was we shared it with some very friendly horses that decided to start eating our gear and tents in the morning.