You can order the permit here : www.environnement.public.lu/guichet_virtuel/escalade/index.html . If you come from far away, you only get 1 day permits.( You might try to come without as there are almost no controls. This is not encouraged!)
The only crag that is not closed for climbing is Berdorf. The rock is sandstone, hard on the surface, soft below. Hold break regularly! Extremly crowded when the weather is good. Some high quality pitches from 5.5 to 5.13.
Getting There
Drive to Berdorf, turn left after you see a Chinese restaurant on your right(if coming from Lux City), follow this road untill it splits, take the left fork, and you come to a parking area. Approach is 10min. From the lower part parking lot you take an obvious trail, and follow it until you go through a 'hole', down a few stairs, and turn left.
The Classics
Mountain Project's determination of some of the classic, most popular, highest rated routes for Luxembourg: