I strongly recommend visiting the Guardian online, and watching the film clips:

Extract from the Guardian:

Herzog has apparently been given permission to film inside the Chauvet-Pont-d'Arc cave, a site in the Ardèche department of southern France that contains the earliest known cave paintings, dating back at least 30,000 years. Even more intriguingly, Herzog is planning to shoot much of the film in 3D.

The Chauvet cave, discovered in 1994, cannot be accessed by tourists, as the French authorities have deemed the risk of degradation to be too high, so Herzog's film might be the only opportunity for the rest of humanity to view the site. The paintings depict lions, panthers, bears, owls, rhinos and hyenas, suggesting a vastly different fauna at the time of the paintings to that of modern France.

"It's a film that I'd like to make because I'm so fascinated about cave art," says Herzog in a series of filmed interviews on the blog, which we've reposted here. "It's still tough to bring equipment down. You are not allowed to touch the wall or the floor or anything. I can have only three people with me, and I can use only lights which must not create temperature. For each shot, because the technology is not really advanced, we had to build own camera from zero using a specific configuration of lenses and mirrors. We are doing something nobody has done with 3D."

Herzog will narrate the film himself, which comes as welcome news. His familiar Teutonic brogue adds so much enthusiastic flavoursome fervour to his documentary films, and the interviews suggest that we're in for another uniquely skewiff vision.

"What is also strange," Herzog reveals, "is that somebody started a painting and then they left. And it's known that 3,500 years later somebody continued the painting. And then a bear that hibernated over it left scratch marks. And over the scratch marks there was man, bear, man, bear, man, bear, man . It's like time does not occur – it's completely fantastic."

Despite his adoption of 3D for the project, Herzog is not an out-and-out convert to the new technology.

"I do it very reduced and as if it was the most natural way to do it," he says. "3D will always have one major problem, and that is when you look as a human being, normally only one eye looks dominantly at things. The other eye is mostly ignored. And only in specific cases - if somebody approaches you - all of a sudden the brain starts to use both eyes for establishing depth of field and understanding space.

"But it tires you when you are a spectator at a 3D movie, because you are forced to see with two eyes and two images superimposed. So 3D, in my opinion, will only work, in my opinion, for the big firework events like Avatar."

It's a fascinating subject matter, but these types of films traditionally suffer from a dry and worthy approach that makes it hard for viewers to truly engage. Herzog offers something more colourful and distinctive, partly because the film-maker himself is just as captivating as his material. And yet he never overwhelms his subject matter. Does the prospect of seeing the film-maker crawling through rocky fissures and uncovering never-before-seen artwork, like some Germanic David Attenborough, have you salivating?

The Cave of Forgotten Dreams - Werner Herzog

http://www.guardian.co.uk/film/filmblog/2010/apr/13/werner-herzog-cave-art-documentary-3d