The first time he was given a tour of the Chauvet Caves in the south of France, filmmaker Werner Herzog knew he wanted to make a documentary about them - and it would have to be in 3D.
"There was a moment when it became clear to me that it had to be in 3D," Herzog says, sitting in the SoHo office of the publicist for his film, Cave of Forgotten Dreams, currently in limited release. "I'd heard so much about the cave paintings, but I thought they would be on flat walls. But there was no element of flatness. They were on these bulbous pendants of rock and in concave niches. The painters utilized the form and drama of the rock for their paintings. So you get a strong sense of drama in the 3D.
"Personally, I'm still mildly skeptical regarding 3D. But part of the audience likes it so you have to take it seriously. The movie industry loves it because admission fees can be higher and, more importantly, it can't be pirated. But some of the films work like July 4 fireworks, which, again, is totally legitimate to do. Still, 3D will never replace all we have in 2D."
Getting permission to film in the closely protected caves took some doing, but Herzog is nothing if not determined. Ultimately, he was given four hours to shoot within the caves.
"I put everything into the battle that was in me," he says. "I was well-prepared and had good arguments. Ultimately, I was also lucky that the French minister of culture was a great admirer of my movies. But that alone would not have been enough to give me the permit."
Even then, Herzog still had to struggle to get the kind of access he felt he needed: "I asked insistently to see the caves before the shoot to see the technical possibilities," he says. "So I was allowed one hour two months before the shooting. That was the moment when it became clear that the movie had to be in 3D."
The cave, Herzog notes, is preserved as "a perfect time capsule": "They have metal walkways and next to you, there are what look like fresh footprints from a cave bear - which have been extinct for tens of thousands of years. We know through radio-carbon dating that somebody made a painting and someone else painted over it - and there were 5,000 years in between. So somebody is completing the painting 5,000 years later.
"All of a sudden, your sense of times starts to spin, as if you're in a vortex."
The German filmmaker, 68, has bounced back and forth between documentaries (Grizzly Man, Encounters at the End of the World) and features (Bad Lieutenant Port of Call, Rescue Dawn) for the past few years.
"Many of my documentaries have been close to fiction films," he says. "Some are scripted, stylized, staged. Some are even feature films in disguise. But in the cave film, I had to stick to what I see."
There is an element of the extreme to all of Herzog's films - extreme conditions, extreme behavior, extreme outcomes. Yet Herzog maintains that the films choose him, not vice versa.
"The films come as they come," he says. "What most urgently pushes me is what I take on next. The films are like uninvited guests, or a burglar who is making a racket in the kitchen. So you have to get up - and you better deal with them."
Most recently, he's been working on a series of short films about people on Death Row.
"The umbrella title I came up with for them was 'Gazing into the Abyss'," he says. "All of a sudden, I realized that could have been the subtitle of all my films. I'm always looking deep into the human soul and the human condition."