I was here in july, just before the TdF passed by on their way to Hautacam.
Luz Ardiden is a HC mountain with 13,5 km of highquality climbing. The villages surrounding it are amazingly beautiful, and if you stay in Luz St Sauveur you have direct access to 3 HC climbs: Col de Tourmalet, Luz Ardiden and Hautacam.
Luz Ardiden is a quite short climb with a few steep sections, some narrow hairpins and a completely stunning view all through the ride and from the top.
The Ariole Climb, in the beginning of the climb - close to the village of Grust is a section that gives you gradients around 10-12,6%
Higher up it's more moderate gradient, and you can enjoy the tremendously beautiful view over Luz St Sauveur and it's surroundings.
Just before the top it gets steeper again, and the hairpins just follow one another.. And then you are up!! And it is just amazing!
Go there! You won't regret one second of it.