There is a series of Cartier-Bresson photos taken at the 1957 Paris 6-Day. They are up to view at the Magnum website. The Meeting took place at the Velodrome D’Hiver and seems to be from the era when “6 Days” meant 6 full days and nights of racing. The Velodrome was destroyed by fire in 1959. It’s also notorious as being the site of the Vel D’Hiv Roundup.