The GR20 runs 180km down the mountainous spine of Corsica from Calenzana to Conca, crossing granite ridgelines, snowfields into early summer and some of the most sustained rugged terrain of any European long-distance trail. It's usually split into a harder northern half and a slightly gentler southern half.
Route map
Terrain
Relentless: steep rocky ascents and descents, scrambling with fixed cables and ladders in places, and long days with little flat ground. Snow can linger on the high passes into June. Well waymarked with red-and-white GR flashes, but the terrain itself demands a good level of fitness and sure footing.
Tips
Refuges (staffed mountain huts) and designated camping areas next to them are the only places to stay or pitch a tent — wild camping elsewhere isn't permitted. Book refuge places ahead in July–August, the busiest period. Many walkers do just the tougher northern half (Calenzana to Vizzavona) as a shorter trip.
Permits & access
No permit needed to walk, but camping is restricted to designated sites next to refuges — wild camping elsewhere on the route is not allowed.