Two of my favourite trans-Andean crossings: From Cuzco to Nazca along the recently paved road via Abancay and on to Chalhuanca, where you can relax in the hot springs before an overnight rest. Over the high plains the next day where you can spot the elusive “suri” woolly alpaca and down to Puquio (try the “gelatina de patita” – trotter jelly with cinnamon) then up again over the Galeras plain, now repopulated with native vicuñas. Finally down a long winding road to the heat of the Nazca desert. Amazing views throughout!
In Chile the well-known lakes crossing is fantastic. A combination of bus, boat, bus, boat, bus to get your from Puerto Varas in the Chile lake district over the Andes all the way to San Carlos de Bariloche on the Argentine side. Stop at the amazing volcanic Petrohue Falls followed by cruising past the picture-perfect Osorno volcano and the magnificent Cerro Tronador – “thundering mountain! – weather permitting. Or you could take the back route from Pucón on Lake Villarica, past the Lalin volcano and drop into San Martin de los Andes in Argentina. Then loop back into Chile via the Lakes crossing.