Few visitors outside of a select group of scientists are allowed into the magnificent Chauvet Cave at all, which contains the world’s oldest known cave paintings dating back some 30,000 years. Werner Herzog, being Werner Herzog, managed to convince the French authorities to let him film inside the fragile and ancient cavern, and the result is astounding. Cave of Forgotten Dreams spends long stretches simply basking in the beauty and detail of these images, and such a film would have been good enough, but Herzog, as ever, probes and questions his subject to penetrate beyond simple documentation. Instead of creating a documentary trying to explain the cave paintings, Herzog accepts that we will never be able to know what life was like for these long-vanished authors. All we are left with is the tiniest traces of their existence, and that in itself we ought to treasure.