Acamarachi, also known as Pili, is a stratovolcano located northeast of the volcanoes Aguas Calientes and Lascar, and southwest of the sector Salar de Pujsa of Los Flamencos National Reserve, in the Antofagasta Region of Chile. The volcano lies on a high plateau called Puna de Atacama.
It has a steep-sided cone with slopes of up to 45 degrees. It is at the southeast end of a small volcano group stretching to Colachi to the northwest. It has an old summit crater with a summit lava flow thought to date from the Holocene era. A small crater lake about 10-15 m in diameter is found within the crater. This is most likely the second highest crater lake in the world, and also the second highest lake of any kind in South America, behind the crater lake of Ojos del Salado.
The volcano was an Inca sanctuary. Metal and textile artifacts have been found, which are exhibited at the R. P. Gustavo Le Paige Archaeological Museum in San Pedro de Atacama.
