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.

Between the Glaciers. Fimmvörðuháls is arguably Iceland's most famous wilderness day hike, a 25km trail that climbs from the coast at Skógar, over a high pass between the Eyjafjallajökull and Mýrdalsjökull glaciers, and descends into the lush Þórsmörk valley. It is widely cited for its 'Waterfall Way'—a series of more than 20 waterfalls along the Skógá River—and for crossing the site of the 2010 volcanic eruption, where trekkers pass the world's two newest craters, Magni and Móði.