In the crater of a semi-dormant volcano in southwest Colombia lies a sacred lake of startling green which used to draw a steady stream of garbage-tossing tourists before Indigenous leaders took back control.

Ascending the Azufral volcano which rises to 4,070 meters (2.5 miles) in the western Colombian Andes is not for the faint-hearted.

It's also not for the uninvited. Only those who receive the nod from the governor of the local Indigenous Pastos community may pass.