The GR20 Corsica. Paddy Dillon

continues running.

      Those who start the GR20 at the beginning of the month and aim to complete it by the middle of the month will experience cold nights and possibly frosts. After mid-October, snow could fall at any time. Snow obscures paths and waymarks, and when it accumulates on steep slopes, there is immediately a risk of avalanche. For ordinary trekkers, the route is closed throughout the winter, although ski-traverses are sometimes achieved.

How to trek

      The main route

      The most straightforward way to trek the GR20 is north to south, on the main red/white flashed waymarked trail from Calenzana to Conca, taking about two weeks to cover the distance. Be sure to build in a couple of spare days just in case they are needed. Note that whenever alternative routes are presented in this guide, the ‘A’ route is the main, or classic, route of the GR20.

      GR20 nord

      It is possible to trek the northern section of the trail from Calenzana to Vizzavona in just over a week, maybe nine or ten days, and experience the most rugged highlights of the route. For those who are confident of their abilities, this is worth considering if time is limited.

      GR20 sud

      Those who are wary of the level of difficulty involved on the higher parts could sample a week on the southern section from Vizzavona to Conca and reserve judgement on the northern section. This stretch also has its tough moments from time to time, so be warned!

      South to north

      Although most people trek the GR20 from north to south, experiencing the toughest sections first, it is also possible to trek from south to north, thereby gradually building up to the most rugged and spectacular parts of the route. An increasing number of trekkers now cover part of the GR20, or all of it, in this direction.

      Alternatives

      Note that there are sometimes high- and low-level alternatives along the way. This provides trekkers with a choice of route. Sometimes the main route is the low-level one, and sometimes the high-level route can be a bit easier than the low-level route. Alternative routes are fully described in this guidebook in exactly the same detail as the main route. Note that whenever alternative routes are presented in this guide, the ‘A’ route is the main route and the ‘B’ route is the variant.

      Links

      Trekkers who complete the whole of the GR20 sometimes regret that they didn’t visit some of the villages off-route. This guidebook includes off-route links with a handful of villages, so that at least a little Corsican culture can be enjoyed. These links also allow trekkers to leave the route if time is limited, with onward transport services mentioned.

      Mountains

      The hardiest enthusiasts could trek the whole of the GR20 and include a handful of mountain peaks along the way. Some of the prominent peaks close to the route can be climbed with a little scrambling. Those trekking the GR20 and climbing a few extra peaks should allow about three weeks. Details of the more popular extra ascents are given in this guidebook, including some of the highest mountains in Corsica.

      Those who follow only the classic course of the GR20 often regret not visiting villages or climbing mountains. This is the summit of Monte Renosu (Stage 11, high-level)

      Guided walking holidays

      A number of companies offer guided treks along the GR20. Approach them with caution, as some operators require you to carry all your kit along the trail. Others may offer baggage transfers, but they may also require you to stay at places far off-route, missing some fine stretches of the GR20. In the north, some operators omit the high-level stages between Calenzana and the Refuge de Carozzu, passing through Bonifatu instead. At the southern end, they may not start and finish at Conca, but at Bavella. If you want to trek the full, classic GR20 as an organised trek, then be sure to question operators carefully to ensure that they are offering the sort of arrangements you really want.

Maps

      The route of the GR20 is well marked throughout. While walking without maps can never be recommended, it is true to say that the waymarking is so good that trekkers might never need to refer to a map for directions. However, this would mean walking in complete isolation from the surroundings, never knowing the names of nearby mountains and valleys, never knowing in advance the shape of the terrain, and never knowing of other route options. To walk without a map is to walk with no real knowledge of your surroundings.

      The best maps of the route are produced by the IGN (Institut Géographique National) at a scale of 1:25,000. These maps have blue covers and belong to a series known as Top 25. Order these in advance of your visit from map suppliers such as Stanfords (12–14 Long Acre, London WC2E 9BR, tel [phone]), The Map Shop (15 High Street, Upton-upon-Severn WR8 0HJ, tel [phone]) or Cordee (3a De Montford Street, Leicester LE1 7HD, tel [phone]). Six sheets are needed to cover the entire route, as follows:

       4149 OT Calvi

       4250 OT Corte and Monte Cinto

       4251 OT Monte d’Oro and Monte Rotondo

       4252 OT Monte Renoso

       4253 OT Petreto-Bicchisano and Zicavo

       4253 ET Aiguilles de Bavella and Solenzara

      The wonderfully compact Didier Richard map of the GR20, using IGN mapping at a scale of 1:50,000, covers the entire route on a single sheet and includes plenty of mountainous terrain off-route. The ISBN is 978-2-344-00043-4, and it is readily available at airport shops, tourist information offices and many other outlets around Corsica. The IGN Mini Corse map, which covers the whole of Corsica at a scale of 1:250,000, is handy to refer to if making long bus or train journeys around Corsica. IGN mapping at all scales can be viewed online at Géoportail, m.geoportail.fr.

      The maps in this guidebook are basically diagrammatic, at a scale of 1:50,000. Transferring the route from these maps to one of the recommended walking maps should be fairly straightforward. The gradient profiles provide an immediate visual appreciation of all the ups and downs along the way.

Mountain weather

      Mountain ranges have a habit of creating their own weather conditions. The mountains of Corsica boast several summits over 2000m (6560ft). In the summer months the sun beats down relentlessly on bare granite slopes, raising the temperature of the air and creating great up-draughts. This draws in cool, moist air from the Mediterranean, leading to condensation, cloud cover, rain and fearsome thunderstorms. The usual pattern is for the day to start sunny and clear, with cloud building up in the afternoon. Whether the cloud eventually results in rain or thunderstorms depends on the amount of build-up. The mountain ridges are very exposed in severe weather conditions and sudden lightning strikes have claimed trekkers’ lives.

      This picture was taken in November. When snow covers the markers, the route becomes very difficult to trace

      Even without thunderstorms the heat alone can be severe at times, causing problems of thirst, dehydration, sunburn and sunstroke. Seasonal streams dry up completely, so that a full day’s ration of water needs to be carried. The recommended minimum is two litres, but three or four may be needed, so take careful note of the availability of water sources in the middle of the day, where these are available. At either side of the peak summer period trekkers can take advantage of cooler, clear conditions.

      The onset of winter sees snow covering the paths, obliterating the trails and waymarks, making most slopes too dangerous to negotiate. Conditions may be truly Alpine. In general, consider the GR20 closed to ordinary trekkers from mid-October to the end of May, although much depends on the severity of the winter months. Bear in mind that it can snow in the mountains in summer, although this is very rare and any snow cover will be very short-lived.

      Weather forecasts, known as meteos, should be