Laguna Verde is surrounded by huge volcanoes: Mulas Muertas, Incahuasi and the monumental Ojos del Salado. At 6893m, this is the highest peak in Chile and the highest active volcano in the world; its last two eruptions were in 1937 and 1956. A popular climb (Oct–March), it takes up to twelve days and is not technically difficult, apart from the last 50m that border the crater. The base of the volcano is a 12km walk from the abandoned carabineros checkpoint on the main road, and there are two refugios on the way up, one at 5100m (four beds, with latrines) and another at 5750m (twelve beds with kitchen and lounge). Temperatures are low at all times of year, so take plenty of warm gear.