By day, the plush green of the Central Andes mountain range dominates the town of Corinto in south west Colombia. By night, the hills shine like Manhattan. Locals call it la Ciudad Perdida, or the Lost City, because what seems to be a mass urban dwelling only appears in the mountains after dark.

But there are no megacities in this part of the world. On the contrary. These mountains host some of Colombia’s most rural and isolated communities. These bright lights are not those of a city, but the flare of the illegal coca and marijuana laboratories, which feed the world’s recreational drug habits.

The Farc guerrillas have demobilised, but coca production – the raw ingredient for cocaine – is booming…