The Défi 24 heures - Passy takes place at the Plaine Joux ski resort, situated above Passy at the base of the Fiz mountain range, with views facing Mont-Blanc. Its central event is La Douze, a 12-hour trail race commencing at 8 a.m. and concluding at 8 p.m. Participants can compete individually or in relay teams.
The race offers access to five marked and secured course routes, featuring pine forests, technical paths, and unobstructed vistas of Mont-Blanc. The event also provides a children's race, live tracking via an app, aid stations operating for the full 12 hours, medical assistance, a secure bag storage area, medals and shirts for finishers, nighttime awards, and the La Douze Fest, an after-race gathering.