Río Los Cipreses National Reserve, National reserve in Machalí, Chile

Río Los Cipreses National Reserve lies in the Andes of the O'Higgins Region, about 50 km from Rancagua, in one of the most glaciated parts of the Central Chilean Andes. A narrow trail fit for mules or horses leads up the valley to the foot of the Cipreses Glacier, where the river still rises directly beneath the ice. Lower slopes carry Valdivian temperate forest, higher ground Southern Andean steppe.

The reserve was established in 1985 by CONAF to protect the natural landscapes and their ecological values. Archaeological discoveries including ancient rock carvings show that people lived in these mountains long before Spanish contact with the region.

The reserve takes its name from the Río Los Cipreses, a tributary of the Cachapoal, and from the cypress stands it protects: some of the northernmost Austrocedrus chilensis in Chile. Along the trails and in the information centre at the entrance, displays on local flora and fauna explain the species and the area's history.

Access is via the Carretera del Cobre to Coya, then a dirt road through Chacayes across the Cachapoal at Puente Chacayes, about an hour from Rancagua; the Ruta del Ácido route passes Termas de Cauquenes. Public transport is extremely limited or non-existent, so a private vehicle is recommended, and a few Rancagua tour operators run trips. Camping and charcoal or wood fires are prohibited; the reserve has six trails of varying difficulty, one accessible for reduced mobility, plus toilets and a small information centre at the entrance.

The reserve holds some of the northernmost stands of Austrocedrus chilensis cypress, a species that normally grows much further south in Chile. This unusual botanical location draws researchers and visitors interested in exploring specialized forest ecosystems rarely found at this latitude.