The stunning blue-green Laguna Verde (4400m) is tucked into the southwestern corner of Bolivian territory, 52km south of Sol de Mañana. The incredible green color comes from high concentrations of lead, sulfur, arsenic and calcium carbonates. Most tours visit this in the morning, but it's at its most dramatic during the afternoon when incessant icy winds have whipped the water into a brilliant green-and-white froth.
This surface agitation, combined with the high mineral content, means that it can remain liquid at temperatures as low as -21.2°C. Behind the lake rises the cone of Volcán Licancabur (5960m), whose summit is said to have once sheltered an ancient Inca crypt.