Puerto Río Tranquilo is a small settlement on the western shore of Lago General Carrera, the vast lake that Chile shares with Argentina, where it is known as Lago Buenos Aires. The water here has a startling colour, a milky turquoise caused by glacial flour, and the lake is so big that the far shore is lost in haze. The village itself is a handful of streets with wooden houses, guesthouses and boat operators, and a population of only a few hundred.
What draws people are the Marble Chapels, the Capillas de Mármol, a set of caves and pillars carved by the lake's waves out of a marble outcrop on the shore. Seen from a small boat, the swirling blue and white walls glow in the reflected turquoise of the water, and in calm weather you can glide right inside the caverns. Mornings are best, when the lake is flat and the light is good, while wind in the afternoon can cancel trips. The surrounding mountains hold the Northern Patagonian Ice Field, and valleys nearby lead to glaciers such as Exploradores.
The road here is the Carretera Austral, and this section from Coyhaique is among its most beautiful. It runs past Cerro Castillo, whose jagged spires stand above the road, then follows the lake shore with great views. Most of it is gravel, with corrugations, loose stones and dust, and long exposed stretches where the wind can be fierce. In rain, the surface turns slick and muddy. Distances between settlements are large, and weather changes fast, so carry waterproofs and warm clothing. The best months are December to March, though even then rain and cold are possible.
Fuel is the thing to plan. There may be a pump in the village, but supplies can run out, so fill the tank in Coyhaique and carry a spare can. There are simple restaurants and guesthouses, though rooms fill quickly in summer, so book ahead. Try lamb cooked over an open fire, fresh trout, and warm bread from a local bakery.