Named one of the “International Film Guide”'s top ten films of 1966-67, A Sunday in Hell is a remarkable chronicle of the Paris-Roubaix bicycle race, described by Leth as “the oldest, the toughest, and the most beautiful of all classical races.” Covering every one of the 273 kilometers of the race, the film has become a classic sports documentary, but is considered, as well, Leth's finest “story” film. He comments:
“My idea of the race was that it was like a novel with many characters, and I had to work out how best to show these characters.... It was like planning a military battle.... I worked out which short cuts to take so that as one camera crew finished at one spot, they could come out ahead of the race and do some more. I had 27 cameramen - each a unit of four men - and I wanted to be everywhere, to catch every story. Somehow it's a kind of madness; all this excitement on those horrible roads on a Sunday in April. But it is extremely beautiful, very true, and very moving.”