The Petrohué River leaves Lake Todos los Santos, a deep green lake at the foot of Osorno, and a few kilometres later squeezes through a channel of black volcanic rock, turning milky-turquoise and loud. This is the Petrohué Falls, not tall but broad and powerful, tumbling through dark basalt that was laid down by eruptions of Osorno in earlier centuries. The contrast between the glacial blue water and the almost black rock is the whole show, and Osorno itself, white-capped and perfectly conical, fills the sky behind.
The falls lie within Vicente Pérez Rosales National Park, the oldest national park in Chile, created in the 1920s. The forest here is temperate rainforest, with huge native trees, ferns and bamboo thickets, damp moss on every surface and the smell of wet earth. Birds are easy to hear and hard to see, and on a quiet day you may catch sight of a woodpecker or a hummingbird. Walking paths lead from the car park to viewpoints over the river, which are short and easy, though the stone can be slippery after rain.
The ride in is the best part. From Puerto Varas the road runs along the shore of Lake Llanquihue, then turns inland toward Ensenada and climbs into the park. It is a pleasant, easy ride, with a good surface and a mix of open views and shaded forest. In summer it can be busy with tour buses, so go early. The volcanoes dominate the skyline, and you will see Calbuco, which erupted dramatically in 2015, sending a huge ash cloud into the sky, a reminder that this is an active volcanic region.
The nearest supplies are in Ensenada, a small village with a few services, but for a proper fuel stop, aim for Puerto Varas, which is well over fifty kilometres away. At the falls there is a small cafe and a craft market selling woollen items, and an entrance fee is charged for the park. Check opening hours, as they vary with the season.
Weather in this part of Chile is unpredictable, with rain, sun and cloud in the same hour. Plan for a wet day and be pleasantly surprised when the clouds lift.