Paris-Brest-Paris, starting from the château park in Rambouillet, is a 1,219 km cyclotourist randonnée to Brest and back. Held every four years, it sees thousands of non-professional long-distance cyclists aiming to finish within a 90-hour limit, not to win by being first across the line. Approximately 6,800 people register, with about 5,100 starting and roughly 4,800 finishing on time. The start is staggered, with riders departing in 27 waves rather than a single crowded group.
The route connects Rambouillet with Brittany via ten stage towns in Normandy and Brittany before returning east. Riders come from around the world, with 71 nationalities represented, including participants from New Zealand, India, Brazil, the United States, China, and Japan. The event relies heavily on volunteers; around 2,500 people assist with course marking, rider welcome, checks, and medal distribution, including about 250 in Rambouillet. While many participants are first-timers, the event also attracts returning cyclists, with two having completed 13 editions. A small youth group, aged 14 to 18, has also completed the challenge accompanied by adult supervisors.