Circuit des 25 Bosses

The 'Circuit des 25 Bosses' (The 25 Bumps) is located in the Massif des Trois Pignons, on the western edge of the Forêt de Fontainebleau. Originally established in the 1970s as a training ground for alpinists, this technical 16km loop remains one of the most demanding day hikes in the Île-de-France region. The trail requires hikers to cross 25 distinct sandstone ridges, involving frequent scrambling over boulders and navigating deep sandy paths. It is an intense physical challenge characterized by constant elevation changes and a unique ecosystem of maritime pines and white sand dunes. Note: Compiled from public sources — not a field report.

Following the historic path used by the Army of the Andes in 1817, this 6-day trans-Andean expedition traverses the central cordillera from Mendoza, Argentina, to the Cajón del Maipo in Chile. The route crosses two significant high-altitude barriers—Portillo Argentino (4,330m) and Paso Piuquenes (4,030m). Hikers move through a high desert landscape of volcanic rock, vast glacial valleys, and the powerful Tunuyán River. The terrain consists primarily of rocky mountain paths, loose scree on the steeper pass approaches, and high-altitude plateaus where exposure to wind and sun is constant.