La Milliacoise is a traditional mountain bike and gravel ride held in Oncy-sur-Ecole, south of Paris in Essonne. The event begins in the morning at the Salle Polyvalente on Chemin de la Ruelle, with participants departing from around 8:00 AM, their start time dependent on the chosen route. Le Club Cycliste de la Vallee de l'Ecole organizes this ride, which is intended for off-road cyclists, not road racers.
The routes traverse the Fontainebleau forest massif and the woodland surrounding Oncy-sur-Ecole, offering multiple options for a shorter ride or a more challenging morning. The mountain bike routes are approximately 25, 35, 45, and 57 km, with elevation gains from about 200 m to 750 m. Gravel riders can select GPX-only routes of around 60 km or 95 km. Now in its 19th edition, on-site registration is available for a small extra fee, and prizes are awarded via a lottery, not solely based on performance.