Coyhaique is the biggest town in Chile's Aysén region, and where the Carretera Austral really starts to feel like a frontier. It sits in a green valley at the meeting of two rivers, the Coyhaique and the Simpson, with steep forested ridges all around and a distinctive pentagonal main square. People here are used to long distances and bad weather, and the town has the practical feel of a place that serves the farms, fishing villages and mountain lodges strung out along the highway.
The Carretera Austral itself is one of the great engineering efforts in Latin America. Built mostly by army engineers from the 1970s through the 1990s, it was designed to connect isolated settlements in Chilean Patagonia that otherwise could be reached only by boat, plane or horse. It runs for about twelve hundred kilometres from Puerto Montt to Villa O'Higgins, a mix of tarmac, gravel and ferry crossings, through temperate rainforest, past glaciers, fjords and blue-green lakes.
South of Coyhaique, the road is a delight and a challenge. There is paved road for some distance, then gravel for long stretches, with loose stone, corrugations, and dust in dry weather, mud in wet. Weather changes quickly, so carry waterproofs and warm layers even in summer. The best months are December to March, when days are long, though rain is still common. Wind can be fierce along open stretches, and traffic is light, so rest stops and mechanics are far apart.
Coyhaique has fuel, supermarkets, banks, workshops and a good range of lodging, and it is the last big place for resupply before the long southern stretches. Fill the tank and carry a spare can before heading south, because the next reliable pumps may be a long way off. Try Patagonian lamb roasted over an open fire, and buy bread and snacks for the road. Check ferry timetables and gravel conditions locally.