As a contributor to TripAdvisor, here is some insight to help you with your travels.
Arrival: There is some parking up the hill or you can park near the town of Les Baux and walk up the hill to the cave. If you are visit Les Baux, get the ticket for the castle and the cave. Last entrance is an hour before closing.
Visiting: You walk in and let your eyes adjust. The quarry is quite large! We enjoyed walking around while the show played before finding a place to sit (bring something to sit on-napkin? Otherwise, your bum will be white powdered). My husband and I spent around an hour just watching the images. The creativity of projecting the images is just amazing. Since we arrived an hour before closing, we could look all around with hardly anyone else around.
This experience is a must see in the area. You will not see anything like this anywhere else!
PS. Bring a light coat or sweater, it is a bit chilly inside.More