Unlike the previous reviewers, I visited the French part of the World Heritage Site, to be more precise the Cirque de Gavarnie. The Cirque is a deep, amphitheatre like valley formed by glaciers, with steep, very high cliffs (the mountains rise up to 1500 meters above the valley floor). It is also home to one of the highest waterfalls in Europe.
I visited the Cirque in July 2020 on a day trip. I stayed overnight in Lourdes and drove by car to the village of Gavarnie (takes about an hour). You are not allowed to enter the village center by car, but there is paid parking near it. I think, the earlier you arrive, the better. In high season, there is the real possibility of traffic jam on the small roads leading to the village. And when I arrived around 10 a.m. the parking was already quite full, too.
Even from the village - provided there are no clouds - you have spectacular views of the Cirque. After an easy hike on dirt roads (duration about one hour), I reached the restaurant at the entrance of the Cirque. From there, you can take several trails. I decided against the path to the waterfall and instead crossed the river and walked past sheep to a snow field at the foot of the rock walls. Much more challenging routes (including through the cliffs up to the Breche de Roland pass) are also available for the more ambitious hikers. But I was already very satisfied with my little hike at the bottom of the valley.
A visit is worthwhile in any case. The landscape is for sure very spectacular (especially compared to the other Pyrenees WHS Madriu-Perafita-Claror Valley in Andorra). However, the Cirque is a major tourist attraction in summer and you won't be the only visitor...