Twelve days in Patagonia: the far south of two countries, and not a tent in sight

Flights from Buenos Aires land in the early afternoon and the approach down the channel is worth a window seat. The town is small and everything below is within ten blocks.

The old convict jail is the reason there is a settlement here at all, and the museum inside it is unexpectedly good: four collections in one building, including a wing left cold and unrestored so you can walk between the cells.

The town museum along the waterfront covers the other side of the story, the Yamana and Selknam peoples of these channels, and the sealers and missionaries who ended them.

The park starts twelve kilometres west and runs to the Chilean border: low beech forest, peat bog, beaver dams and small bays opening onto the channel. It is gentle country and completely unlike anything further north.

The narrow gauge railway was laid by the prisoners to haul timber back to the jail. The rebuilt tourist version runs forty five minutes along the same roadbed into the park, with a commentary explaining what the men were doing out here.

Inside, the walking is easy and the coast path is the best of it. Ruta 3, the road that begins in Buenos Aires, ends at Bahia Lapataia with a sign giving the distance back, and everybody photographs it.

The channel was surveyed by HMS Beagle in the 1830s with Darwin aboard on the second voyage, and it is still the best way to understand the geography: a deep waterway between two mountain walls, Argentina to the north and Chile a few kilometres south.

Boats leave the tourist pier through the morning. Four hours takes in the sea lion colony, an island of cormorants and Les Eclaireurs, the small red and white lighthouse that everyone here calls the last one. It is not the lighthouse Jules Verne wrote about, and nobody is in a hurry to correct you.

In the afternoon, if the wind allows it, walk up to the Martial glacier directly above the town. What is left of the ice is small and shrinking; the view down over the roofs to the channel is the reason to go.

The flight from Ushuaia to El Calafate takes about an hour and a quarter and crosses the whole southern icefield on a clear day, which is worth the left-hand window.

El Calafate is a single long street of outdoor shops, chocolate and lamb restaurants on the edge of a very large milky lake. It is a service town and an honest one.

Spend the afternoon at the Glaciarium, a few kilometres out of town. It explains how the Southern Patagonian Ice Field works, why Perito Moreno behaves differently from almost every other glacier on earth, and what the ice you will stand in front of tomorrow is actually doing. Half the people who go to the glacier without this see a big white wall; the ones who came here see a river.

Buy tomorrow's lunch tonight. There is one overpriced cafe at the glacier.

Eighty kilometres west of town, a glacier five kilometres wide comes down off the icefield and pushes into Lago Argentino, ending in a wall of ice about sixty metres above the water. What makes it different from almost every other glacier in the world is that it is not retreating, and what makes it unforgettable is that it calves constantly.

The park has built several kilometres of steel walkways on the peninsula opposite the front, at four levels, and you can spend six hours moving between them. The noise comes first, a crack like artillery, and then a tower of ice the size of a house drops into the water. It happens every few minutes.

Every few years the advancing ice dams an arm of the lake against the shore, the water backs up behind it, and the dam collapses in an arch. Nobody can predict when.

Buses leave El Calafate in the morning and come back late afternoon, so you get a full day. Boat trips run from a jetty below the walkways to the front of the ice, and there are ice treks on the glacier itself that must be booked well ahead.

Three hours north on a paved road along Lago Viedma, with Fitz Roy visible from about forty kilometres out on a clear day and completely invisible on a bad one. Coaches run several times daily and most of them arrive around lunchtime.

El Chalten was founded in 1985, which makes it younger than most of the people walking through it. Argentina built it to establish a presence during a border dispute with Chile and it has one street, a park office at the entrance where the rangers brief every arrival, and trailheads at the end of the road.

Stretch the legs this afternoon on the two short climbs behind the park office. They take two hours between them and they give you the whole valley, the town below and, if the cloud lifts, the Fitz Roy range.

This is the walk people come to Argentina for. Eight hours there and back from the edge of the village, about twenty kilometres, easy for most of its length through beech forest and along a river, and then a final kilometre of relentless steep scree that gains four hundred metres and takes an hour.

At the top, without warning, you come over a lip onto a cobalt lake with Fitz Roy standing directly behind it, three thousand four hundred metres of vertical granite that mountaineers rate among the hardest big walls anywhere. On a clear day it is one of the great views on earth. On a bad day you will see cloud and you will still have earned your lunch.

Start at seven. Take at least two litres of water, food, and layers, because the top is exposed and cold whatever the valley is doing. There is no shelter and no water on the final climb.

Come down slowly. The scree is worse descending than climbing and this is where ankles go.

Gentler than yesterday and almost as good. Six hours return, mostly flat, along a valley to a grey glacial lake with icebergs in it and Cerro Torre standing behind, a needle of granite with a permanent mushroom of rime ice on the summit.

Cerro Torre is only just over three thousand metres and it was not climbed until the 1970s, long after every eight-thousander in the Himalaya, which tells you what the rock and the weather here are like. The first claimed ascent in 1959 is still argued about.

The lake is exposed and the wind funnels down the glacier, so the mirador above it is a five minute climb worth making and a ten minute stay.

Back in time for a late lunch, which is the right way to spend your last afternoon here.

The longest travel day of the trip: south past El Calafate, west across the steppe, over the border at Cerro Castillo and down into Chile, somewhere between nine and eleven hours depending on the queue. Scheduled buses do it with a change; a hire car needs paperwork arranged days earlier.

Eat everything fresh before the frontier. Chile confiscates fruit, meat, dairy and honey, and fines people who forget.

The country changes as you cross: the Argentine side is flat yellow grass with guanacos on it, and then the Paine massif appears on the horizon like something dropped there.

Break the drive at the Cueva del Milodon, twenty minutes north of Puerto Natales. A two hundred metre cavern in a limestone hill, where in the 1890s a settler found a piece of skin with hair still on it belonging to a mylodon, a ground sloth the size of a small car that died out here around ten thousand years ago. The find set off a scientific scramble to see whether any were still alive. Bruce Chatwin's In Patagonia opens with a scrap of that skin in his grandmother's cabinet.

The park's namesake walk and its hardest day trip: roughly nine hours on the move and eight hundred metres of climb, from the Hotel Las Torres area up a windy valley, through a beech forest, and then up an hour of boulder field that has broken better people than you.

The reward comes all at once. You come over the moraine and the three towers are directly in front of you across a green lake, vertical, absurd, close enough to feel the cold coming off them. Most people sit there for an hour whatever the wind is doing.

Start early, take everything you need, and check the forecast the night before: this is the walk most worth moving to a clear day. Rangers close it in high wind and they are right to.

There is a refuge partway up that sells food, which is the one place on this route where you do not strictly have to carry lunch.

Grey is where the Southern Patagonian Ice Field, the third largest body of ice on the planet after the two polar caps, spills into the park. The glacier front is several kilometres wide and the lake below it is full of icebergs that drift down and beach themselves on a black sand bar at the southern end.

The easy version is the walk out onto that sandbar from the ranger station at Lago Grey, which takes an hour and puts you next to stranded ice the size of a bus. The better version is the boat, which crosses the lake to the glacier front and back in about three hours, weather permitting.

The best version is the catamaran to Paine Grande and the walk up to the Mirador Grey, which looks down the length of the glacier from above. That is a full day and it is the third arm of the W.

Whichever you choose, keep the afternoon for driving the park roads. The lakes here are extraordinary colours and there are guanacos on every ridge, along with a real if slim chance of a puma at dusk.

The road out of the park on the eastern side runs along Lago Sarmiento, a long lake with a white rim where calcium has been deposited on the shore in bands, and the whole massif behind it. It is the last look and the best angle on it.

Guanacos are thickest along this stretch in the morning, and so are the condors above the ridges. There is no walking to do; stop at the pull-ins and take the time.

Punta Arenas is about five hours from the park gate and Puerto Natales about two, so an evening flight north is comfortable and a morning one is not. If you have a spare afternoon in Punta Arenas, its cemetery and the wool barons' mansions on the main square explain everything about how this end of the continent was settled and by whom.