The GR20 doesn't have its reputation by accident. From the very first kilometers out of Calenzana, the trail climbs relentlessly toward the Carozzu refuge through a chaos of boulders and thorny scrubland. Guides routinely rank it as the toughest long-distance trail in Europe — not because of altitude (the highest point barely clears 2,700 meters), but because of the terrain: raw granite, brutal cumulative elevation gain, and constant exposure to the elements that leaves almost no real rest over fifteen days.
What truly sets the GR20 apart from a Pyrenean GR10 or an Alpine GR5 isn't just technical difficulty. It's logistical isolation. Over long stretches there's no access road to resupply or evacuate an injured hiker — everything runs through the refuges, with rescue helicopters as the last resort. The refuge network is managed by the Parc Naturel Régional de Corse (PNRC), and unlike many other GR trails where you can pitch a tent wherever you fancy, wild camping here is banned outright — only camping "in the immediate vicinity" of refuges, in designated zones, is allowed. That constraint shapes the entire trip: you don't wander freely, you move from stage to stage, with spots that need booking ahead of time.
The northern section, from Calenzana to Vizzavona (roughly 90 km, plan on 8 to 9 days depending on your pace), is the most technical. The passages through the Aiguilles de Bavella or the crossing of the Rinaghja plateau demand solid experience with alpine terrain. It's not unusual to be scrambling hands and feet on the cabled sections, with a drop below you and the wind doing you no favors. The reward matches the effort: rose-granite cirques that evening light turns into natural cathedrals, and a mineral silence you won't find in any other French mountain range.
Logistics are where a good chunk of the trek's success gets decided. Refuge bookings are made online through the PNRC's official system, and spots are strictly limited — a fully booked refuge won't budge, no matter how much you plead. Booking-opening dates for the following season shift from year to year, so it's worth checking the park's website directly a few months before you leave rather than trusting a fixed calendar. Budget realistically too: refuge nights, half-board or meals bought on site, transport to and from Corsica, and a return trip from Conca or Vizzavona if you split the trek into two parts — an increasingly common choice for those who can't free up fifteen straight days. Rates change every season, so again, the PNRC website is the most reliable source.
The southern section, from Vizzavona to Conca (roughly 6 to 7 days), turns more varied — Laricio pine forests, high-altitude sheepfolds where you can sometimes buy local cheese or charcuterie, and glacial lakes of an almost unreal blue, like Nino or Capitellu. This is where the trek takes on a more contemplative feel, once your legs have found their rhythm and your mind has synced with the mountain's pace. It's also, paradoxically, the section where heat becomes the main enemy: less altitude, less wind, and stretches where water sources thin out noticeably at the height of summer. Fill your bottles at every spring or refuge you pass, and never head out under-equipped on stages flagged as dry — some south-facing ridge crossings offer no water at all for several hours.
"On the GR20, every day you want to quit. Every evening, you remember why you didn't."
Managing your daily pace matters as much as physical preparation. Afternoon storms are a recurring reality on Corsican ridgelines in summer: starting early, ideally before sunrise on the longest stages, means you're already off the ridge or under cover by the time the sky turns in early afternoon. Rigid, deeply lugged boots aren't a luxury here but a necessity on granite that's just as slick dry as wet. Mid-June or mid-September is the window regulars recommend most: refuges are less packed than at the height of summer, and daytime heat is gentler, even though nights at altitude can stay cold year-round.
On the last day, descending toward Conca, the sea appears between the pines. It isn't an ending — it's a synthesis. Fifteen days of rock, wind, fatigue, and raw beauty all condense into that distant strip of blue. The GR20 doesn't leave you unchanged. It hands you back to yourself, slightly different from the person who left Calenzana two weeks earlier — and likely far more attuned to what a simple trail can demand of a body and a mind.