Seven weeks overland from the Peruvian coast to the Brazilian one, crossing the Andes twice and the Altiplano once. The order is dictated by altitude: Lima at sea level, then Cusco to acclimatise, then Puno, La Paz and the salt flats — each one higher than the last — before dropping into Chile and running south to Patagonia.
The route is closed end to end. Every bed and every flight is booked, Zurich to Zurich, including the way home on 8 November — fourteen stops in five countries, plus the flights out of Zurich on 22 September and back into it on 9 November. One ground transfer is still to arrange.
The parts that are actually hard
The Uyuni crossing is the hinge. A three-day jeep tour out of Uyuni ends at the Hito Cajón border post and drops you in San Pedro de Atacama — the tour is the way into Chile, so there is no separate border leg to book and no fallback if it doesn’t run.
The second night of that tour is a refuge at Laguna Colorada, around 4,300 m. That is why La Paz gets a full rest day at 3,600 m first, and why Cusco gets four nights before anything else. The whole first half of the route is really an acclimatisation schedule with sightseeing attached.
Patagonia is tight rather than high. The flight into Puerto Natales lands mid-afternoon on the 23rd and the bus out leaves on the 25th, which makes the 24th the only day in Torres del Paine — a single full-day circuit, booked, with no second attempt if the weather closes in.
Ten flights, nine of them cabin-bag only, across a route that runs from −20 °C in an unheated refuge at 4,300 m to +30 °C at 88 % humidity in Rio. One layering system has to cover all of it, and nothing gets packed for a single day.