Torres del Paine O Circuit

The W and the O share the same famous valleys, but the O is the bigger trip. The W traces three arms on the southern face of the massif and takes four or five days. The O wraps the entire Paine massif in a single loop, adding the remote, little-walked back side before joining the W for its final stretch, and most people take seven to nine days over it. The other big difference is your pack. On the W the hardest climbs, such as the base of the towers, are usually done as day walks from a fixed camp, while on the O you carry everything with you the whole way round. Choose the W if you are shorter on time or want a first taste of Patagonia on well-serviced trails. Choose the O if you want solitude, the wild lenga forests and river valleys of the back side, and the moment you crest the John Gardner Pass to a sudden view over the Southern Patagonian Ice Field, and you are happy to commit to more days and a heavier load.

The season is short and runs from roughly November to late March, sometimes into early April. The back side of the loop opens later and closes earlier than the W, because the higher, more exposed ground around the John Gardner Pass needs the deep snow to clear and the small back-country camps only staff up for the core months, so the O has a narrower window. December to February is the warmest stretch with the longest daylight, and also the busiest and the windiest. Late November and March are quieter, and the autumn colour on the back side in March is superb, though services are thinner and the weather less settled. Whenever you go, expect Patagonia to serve all four seasons in a single day, with strong wind the near constant, so plan around the conditions rather than the calendar.

The gateway town is Puerto Natales, where the gear shops, supermarkets and trailhead buses are. Most people fly into Punta Arenas first and take a bus a few hours north to Puerto Natales. From there, daily buses run into Torres del Paine during the season and stop at Laguna Amarga, the entrance for the Las Torres sector where the O begins and ends. Because the loop is walked counter-clockwise, you set off north towards Seron rather than up to the towers, saving the towers for the very end. Buy your park entry ticket online in advance through the national park system, as it is checked when you arrive.

Yes, and it is the single biggest planning task for the O. Every night inside the park must be reserved before you arrive, whether you want a refugio bed, a serviced campsite or a pitch for your own tent, and wild camping is not allowed. The complication is that three different parties run the stops. Vertice Patagonia handles the back side and western camps such as Dickson, Los Perros, Grey and Paine Grande, Las Torres Patagonia, formerly Fantastico Sur, runs Seron and the eastern camps around Central, Chileno, Frances and Cuernos, and the park authority CONAF manages a couple of free, basic sites. Because the O runs one way, the real task is booking every night in the correct counter-clockwise order, with no gaps, across those separate systems. Reservations open a few months ahead of the season, often around April or May, and the scarce back-country nights such as Los Perros and Dickson go first, so book as early as you can. Traileasy's planner sets out your nights in walking order and shows which camp each day ends at and which of the parties to book it with, so you can line up the whole chain before the tight back-country nights are gone.

Most hikers take seven to nine days, with eight the common choice, and that pacing gives you slack for weather and for the longer days on the back side. The direction, though, is not a choice. The park requires the full circuit to be walked counter-clockwise, so you start north towards Seron and Dickson and approach the John Gardner Pass from Los Perros. The pass is crossed in that one direction for safety and to keep people moving on a steep, weather-exposed climb with an abrupt descent to Grey Glacier on the far side, and rangers check that you are travelling the right way and keeping to your booked camps. Walking it counter-clockwise also builds the trip towards its finale among the celebrated valleys of the W and the towers on your final morning.

The main loop is a single, well-trodden line and is signed at the junctions, so on a clear day it is hard to lose. The back side is where navigation matters more than on the W, as you are far from other hikers for long stretches, the camps are spread out, and cloud or snow around the John Gardner Pass can swallow the landmarks fast, so it is worth carrying navigation you can rely on rather than a phone signal you will not have. The free Traileasy app keeps offline maps on your phone and follows the exact route you planned, even on the remote back side where there is no reception. If you would rather use a dedicated device, you can also export your planned route to GPX and load it onto a GPS watch or another navigation app.

The O is a strenuous multi-day trek rather than a technical climb. There is no altitude to worry about and no scrambling, but the days are long and consecutive, you carry a full pack the whole way, and the John Gardner Pass day is a genuine test, with a sustained climb and a steep, rough descent to Grey Glacier. The back side is remote, so a bad-weather day out there is harder to bail out of than on the W. You do not need mountaineering skills or prior expedition experience, but you should be comfortably fit, able to walk day after day for many hours under a loaded pack, and ready for wind, rain and cold at any time. A few months of regular hills and back-to-back training walks before you go make the difference between enduring the O and enjoying it.

Pack for all four seasons, because you will meet them, and pack for more self-sufficiency than the W. The essentials are a windproof and waterproof shell, warm insulating layers even in summer, quick-drying base layers, sturdy broken-in boots, and a warm hat and gloves for the cold, exposed pass. Trekking poles help in the wind and on the steep descent from the pass, and strong sun protection matters when the Patagonian sun does appear. The back side has fewer places to top up supplies, so plan your food to carry further between stops, though water from the streams along the route is generally safe to drink and a refillable bottle saves weight. If you are camping and would rather not fly with a full kit, Puerto Natales has shops such as Erratic Rock where you can rent tents, sleeping bags and stoves.