Directed by Werner Herzog G cert, Cineworld/IFI, Dublin, 90 min

THIS DELIGHTFUL documentary is, by the standards of its eccentric creator, a relatively conventional project. A film about French cave paintings is, after all, just the sort of thing you’d expect to see on the National Geographic Channel at tea time. However, the director in question is Werner Herzog, so all usual notions of conventionality go out the window.

The great German, whose career remains more robust than any of his contemporaries, has taken the unusual step of shooting the film in 3D. You couldn’t quite say he makes an unanswerable case for the much-criticised process, and the novelty still wears off after 20 minutes. But the addition of depth helps demonstrate the extent to which such the prehistoric artists used natural contours to flesh out their pictures of lions, bears and horses.

Cave of Forgotten Dreamsdeals with paintings in the Chauvet Cave, near the Ardeche River, which, by some experts' reckoning, could be the oldest such artworks in existence. Rediscovered in 1994, the paintings had, thanks to a rock fall some 25,000 years ago, remained unseen since the Stone Age.

Not surprisingly, the French authorities have gone to extreme lengths to protect the works. Walkways have been laid down. The paintings can only be viewed from a distance. It reflects particularly well on the curators that, when selecting a film-maker to document the finds, they picked the director of Aguirre, Wrath of Godand Fitzcarraldo.That's creative thinking.

The defining feature in Herzog’s recent documentaries has been the director’s own, rumbling, amused, occasionally pedantic voiceover. Here, he almost sounds excited (though not exactly happy, of course) as he talks us through the astounding origins of the paintings. It fairly boggles the mind to consider that the pieces, which Herzog sees as a “form of proto-cinema”, were touched up and added to over centuries. All conventional time frames are redundant.

So, Cave of Forgotten Dreamsis just a traditional, if very fine, documentary that happens to have been shot in 3D? Fret not, Herzogians. A coda concerning albino crocodiles is as odd as anything in the great man's distinguished oeuvre.