France — Calvi
Corsica's GR20 Northern Half is a truly formidable 80km traverse across the island's rugged crystalline spine. This very challenging 7-9 day route plunges through dramatic highlands and across exposed ridges, demanding sure-footedness and stamina. Expect steep ascents, technical scrambles, and breathtaking panoramas on this legendary French trail.
Distance: 80.0 km
Elevation Gain: 6000 m
Difficulty: Very Challenging
Duration: 7-9 days
The GR20 (Grande Randonnée 20) is widely regarded as the most difficult long-distance trail in Europe, a legendary route that bisects the Mediterranean island of Corsica along its jagged crystalline spine. While the full trail stretches approximately 180 kilometres from Calenzana in the north to Conca in the south, it is the Northern Half—the section from Calenzana to the mountain pass of Vizzavona—that holds the most fearsome reputation. Spanning roughly 80 kilometres with a staggering 6,000 metres of vertical ascent, this segment is a relentless sequence of steep granite ridges, technical scree slopes, and exposed alpine plateaus. It is not merely a walk; it is a high-altitude odyssey through a landscape of prehistoric intensity, where the scent of the maquis shrubland meets the thin, cold air of the Monte Cinto massif.
The Northern Half is defined by its uncompromising terrain. Unlike many continental European trails that follow gentle valley floors, the GR20 North stays high, often hugging the ridgelines and requiring trekkers to use their hands for balance on frequent scrambles. The rewards, however, are commensurate with the effort. Trekkers are treated to views of the turquoise Mediterranean shimmering in the distance while standing amidst snow-flecked peaks, glacial lakes like Lac de Capitello, and ancient forests of Laricio pines. This is a journey for the physically prepared and the mentally resilient, offering a profound sense of isolation and achievement in one of the last true wildernesses of Western Europe.
The GR20 Northern Half is a masterclass in verticality. From the moment you leave the village of Calenzana, the trail wastes no time in ascending into the high mountains. The geology of the north is dominated by granite and schist, creating a landscape of sharp needles (aiguilles) and deep, shadowed cirques. The path is often indistinct, marked by the iconic red-and-white blazes of the French GR network, but the terrain itself is the primary navigator. You will find yourself traversing narrow ledges, navigating boulder fields where every step must be calculated, and descending steep "casse-cou" (neck-breaker) slopes that test the durability of both boots and knees.
One of the defining characteristics of the Northern Half is the "stage" system. The trail is traditionally broken into nine stages, each ending at a refuge managed by the Parc Naturel Régional de Corse (PNRC). These refuges are strategically placed near the only reliable water sources in the high mountains. Because wild camping is strictly prohibited to protect the fragile ecosystem and prevent forest fires, the rhythm of the trek is dictated by these mountain outposts. This creates a unique social atmosphere; despite the physical hardship, there is a shared camaraderie among the "GR20ists" who gather each evening to share stories of the day's climb over bowls of Corsican lentil soup.
The climate adds another layer of complexity. While Corsica is a Mediterranean island, the GR20 North is a high-alpine environment. Even in mid-summer, temperatures can plummet after sunset, and the island is notorious for its "orages"—violent afternoon thunderstorms that can turn dry granite into a slippery, dangerous hazard within minutes. Trekkers must be prepared for intense heat in the valleys and freezing winds on the passes (cols). The Northern Half is also home to the highest point on the island, Monte Cinto (2,706 m), which can be summited as a challenging detour from the main route. This section of the trail is not just a physical test; it is a sensory immersion into the rugged soul of Corsica, far removed from the glitzy beaches of the coast.
The GR20 is a relatively modern creation, but the paths it follows are ancient. For centuries, these mountain tracks were the exclusive domain of Corsican shepherds practicing transhumance—the seasonal movement of livestock between lowland winter pastures and high-altitude summer grazing lands. The stone ruins of "bergeries" (shepherd huts) scattered along the trail are silent witnesses to this pastoral history. These shepherds, known for their fierce independence and deep knowledge of the terrain, carved out the routes that now form the backbone of the trek.
The formalisation of the GR20 began in the late 1960s and early 1970s. It was the brainchild of Michel Fabrikant, a French mountaineer and writer who envisioned a continuous traverse of the island's mountain crests. In 1972, the trail was officially inaugurated by the PNRC. Fabrikant’s goal was to create a route that showcased the interior of Corsica, which at the time was being abandoned as the population shifted toward the coastal cities. By bringing hikers into the mountains, the trail helped revitalise the highland economy and provided a reason to preserve the unique Laricio pine forests and endemic wildlife, such as the Mouflon (a wild mountain sheep) and the Bearded Vulture.
Culturally, the GR20 is deeply tied to Corsican identity. The island, often called the "Mountain in the Sea," has a history marked by resistance and a strong sense of local pride. The trail passes through regions that were once strongholds of Corsican independence movements. Even today, the language heard in the refuges is often Corsican (Corsu), a Romance language closely related to Italian. Trekkers are encouraged to respect this heritage by learning a few words of the local tongue and appreciating the traditional products—such as Figatellu (liver sausage) and Brocciu (sheep or goat milk cheese)—that are still produced in the mountain villages and served at the refuges. The GR20 is more than a hike; it is a journey through the living history of a rugged, resilient people.
Want more background? Read extended notes on history and cultural context → Learn more
The window for safely attempting the GR20 Northern Half is relatively narrow, dictated by the presence of snow in the high passes and the availability of services at the refuges. The official season runs from late May to early October, but each month offers a distinct experience and set of challenges.
June: This is arguably the best time for the trek. The days are long, the mountain flowers are in full bloom, and the water sources are at their peak. However, snow can often linger in the high couloirs and north-facing slopes until mid-June, particularly on the Cirque de la Solitude bypass or the ascent of Monte Cinto. Trekkers in early June should be comfortable with snow travel and may need to carry lightweight crampons or an ice axe depending on the previous winter's snowfall.
July and August: These are the busiest months. The weather is generally stable, but the heat can be oppressive, especially during the steep climbs out of the valleys. Afternoon thunderstorms are a significant risk; they typically build up around 2:00 PM or 3:00 PM, making early starts (often at 5:00 AM) essential to ensure you are off the high ridges before the lightning begins. The refuges are often crowded, and water sources can begin to dry up, though the main PNRC huts usually have reliable supplies.
September: A favourite for experienced trekkers. The crowds thin out, the temperatures become more manageable, and the light has a crisp, golden quality perfect for photography. The risk of snow returns toward the end of the month, and the days become noticeably shorter. By late September, some of the private bergeries may begin to close, though the main PNRC refuges remain guarded until early October.
Winter (October to May): Outside the guarded season, the GR20 North becomes a serious mountaineering undertaking. The trail is covered in deep snow, the red-and-white markers are buried, and the refuges are left in "winter mode" (unheated, no food, no gas). Only those with advanced winter navigation and alpine survival skills should attempt the route during this time. Avalanche risk is high in the steep cirques of the north.
Day 1: Calenzana to Refuge d'Ortu di u Piobbu
Day 2: Refuge d'Ortu di u Piobbu to Refuge de Carozzu
Day 3: Refuge de Carozzu to Asco Stagnu
Day 4: Asco Stagnu to Refuge de Tighjettu
Day 5: Refuge de Tighjettu to Refuge de Mori
Day 6: Refuge de Mori to Refuge de Manganu
Day 7: Refuge de Manganu to Refuge de Petra Piana
Day 8: Refuge de Petra Piana to Refuge de l'Onda
Day 9: Refuge de l'Onda to Vizzavona
Important Notes:
The GR20 North requires a level of physical preparation that exceeds most other European treks. You should be comfortable carrying a 12–15 kg pack over steep, uneven terrain for 6–9 hours a day. Training should include significant elevation gain and descent to toughen the knees. Logistics are relatively straightforward but require coordination: most trekkers fly into Calvi or Bastia and take a bus or taxi to the trailhead in Calenzana. It is highly recommended to spend a night in Calenzana to acclimatise and start early the next morning.
Booking coordination is vital. The PNRC refuges have limited space and must be booked months in advance. If you plan to use the train to exit at Vizzavona, check the Chemins de Fer de la Corse (CFC) schedules, as they can vary seasonally. Base yourself in Calvi for a few days before the trek to enjoy the beach and finalise your gear; it is a well-equipped town with several outdoor retailers.
Accommodation on the GR20 North consists of PNRC-managed refuges, private bergeries, and designated camping areas surrounding the refuges. Wild camping is strictly prohibited throughout the Regional Natural Park of Corsica.
Refuge Facilities:
Camping:
Costs and Availability:
There is no "permit" required to walk the GR20 in the sense of a restricted entry pass. However, because wild camping is illegal, your "permit" is effectively your refuge or campsite reservation. The PNRC (Parc Naturel Régional de Corse) manages the booking system, and it is mandatory to book your accommodation in advance if you intend to stay in the refuges or use their rental tents.
Booking Process:
Logistics and Fees:
Detailed route notes, maps, logistics & tips for the Gr20 Northern Half (PDF).
Precisely traced GPX for the Gr20 Northern Half, ready for your GPS or favourite mapping app.
Corsica offers a wealth of experiences beyond the high peaks of the GR20. Consider these options before or after your trek:
Weather Hazards: The most significant danger on the GR20 North is the weather. Afternoon thunderstorms (orages) are frequent and violent. Lightning is a genuine threat on the exposed ridges. If you see clouds building, descend from the ridgeline immediately. Additionally, the "Mistral" and "Libeccio" winds can reach gale force, making narrow ridges dangerous. Always check the Meteo France mountain forecast (displayed at every refuge) before setting out.
Terrain and Physical Injury: The trail is exceptionally rocky. Ankle sprains and knee strain are the most common injuries. The granite slabs of the Spasimata and the scree slopes of Monte Cinto require constant focus. Dehydration and heatstroke are risks in the lower valleys; start your day at dawn to complete the hardest climbing before the midday heat.
Water Safety: Do not rely on seasonal streams marked on maps, especially in late summer. Only the springs at refuges and bergeries are guaranteed. Always treat water from non-tap sources. Carry a minimum of 3 litres of water on every stage.
Emergency Services: Mobile phone signal is extremely spotty and non-existent in many deep valleys. In an emergency, the international number is 112. However, you may need to send someone to the nearest refuge to alert the warden, who has radio contact with the PGHM (Peloton de Gendarmerie de Haute Montagne), the elite mountain rescue unit. Helicopter evacuations are common on the GR20 but should only be summoned for genuine emergencies.
Fire Risk: Corsica is extremely prone to wildfires. Smoking is discouraged on the trail, and open fires are strictly prohibited. Be extremely careful with camping stoves and only use them in designated areas at the refuges.
Monte Cinto Summit: At 2,706 metres, Monte Cinto is the highest peak in Corsica. The modern GR20 route passes very close to the summit at the Pointe des Eboulis. The detour to the actual summit takes about 1.5–2 hours return and involves some light scrambling. On a clear day, you can see the entire island and even the coast of Italy and the French Alps.
Lac de Nino: Located on Stage 6, this is one of the most iconic sights in Corsica. The lake is surrounded by "pozzines"—deep, water-filled peat bogs that create a vibrant green patchwork. Wild horses often graze here, and the flat terrain provides a rare moment of easy walking and reflection.
The Spasimata Suspension Bridge: A 30-metre long bridge that swings over a dramatic waterfall and canyon. It is a highlight of Stage 3 and a favourite spot for photography, though it can be intimidating for those with a fear of heights.
Lac de Capitello and Lac de Melo: These two glacial lakes are visible from the high ridge on Stage 7. Capitello is the deepest lake in Corsica (42 m) and is often frozen well into the summer. The view from the Breche de Capitello, looking down at the deep blue water framed by jagged granite walls, is arguably the most spectacular on the entire trail.
Cascade des Anglais: Located near the end of the Northern Half in the Vizzavona forest. These beautiful waterfalls and crystal-clear pools are a popular spot for a final swim before reaching the village. The name comes from the English aristocrats who used to holiday in Vizzavona during the 19th century.
The GR20 passes through the Parc Naturel Régional de Corse, a protected area home to rare endemic species. With thousands of hikers traversing the trail each year, the environmental impact is significant. It is the responsibility of every trekker to minimise their footprint.
Leave No Trace Principles on the GR20:
