Ultra Randonnée 13 guides participants around the Étang de Berre, a large saltwater lagoon west of Marseille in Bouches-du-Rhône. This endurance-walking challenge is organized by the Bouches-du-Rhône hiking committee, starting in Saint-Chamas with support points near Marignane and Miramas. The main event covers approximately 122 to 124 kilometers, completed in a single continuous effort over day and night, meaning many participants are walking for over 40 hours throughout the weekend. Shorter options are typically offered, such as a 54 km half-circuit and a two-person relay divided into legs of roughly 70 km and 54 km.
The course follows a straightforward concept: complete the full circuit of the Étang de Berre on foot, primarily utilizing the GR 2013 trail. Participants will see the port of Saint-Chamas, views towards Martigues, the Rognac plateau, the beaches of Istres and Figuerolles, and the vineyards of Château Virant. A notable part of the experience is the night passage across the Jaï, the narrow land bridge separating the lagoon from the sea. This is not a quick race with a simple conclusion; it is a lengthy ultra-randonnée where fatigue, navigation, walking through the night, and perseverance are integral to the challenge.