We enter the city of La Paz and find ourselves in a place where lurking just beneath the veneer of an ordinary large city there are strange stories, mysterious behaviours and rituals from a different era. This is a city where dozens of witches still practice, where shrivelled animal embryos are on sale, where families buy human skulls and keep them in their home for good luck, where a museum celebrates and documents the history of cocaine, where public transport is a network of cable car lines. After all these years of knowing smugly that La Paz is the highest capital city in the world, it turns out that it’s…