The Trail Auffargis begins in Auffargis, a village in the Yvelines department of Île-de-France. It directs runners into the Rambouillet forest in mid-March. ASR Trail 78 organizes this series of wooded trail runs within the Haute Vallée de Chevreuse Regional Natural Park. The event offers a 15 km night race, a 26 km short trail, and a 45 km long trail.
The night race commences at 7:00 PM, covering 15 km with approximately 400 m of elevation gain. The 26 km course features about 700 m of gain, and the 45 km course includes around 1,200 m. Participants can also compete in combined challenges. The short challenge links the night race with the 26 km event, and the long challenge combines the night race with the 45 km course. This structure provides multiple race opportunities over the weekend, particularly for those seeking forest trails both after sunset and the following morning.