Matteo Pelucchi (IAM) beat Marcel Kittel (Giant Alpecin) into second in a sprint finish but only a handful of riders were able to coast home without alarm.
As the video above shows, a monstrous crash brought down scores of riders and ended up blocking the whole road.
Early Mur move not enough for Flèche first timer Roglic
No serious injuries were announced.
The race director told AFP: “There is no news of serious injuries.”
You can relive the final moments of the crazy race with full commentary below.
Kittel, who was wearing the yellow jersey on stage two, tweeted about his near miss as he actually rode over a competitors bike to avoid injury.
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Flèche Wallonne 2021 Men's Highlights - Catch up with every moment from a sensational race