Man in brown jacket and black pants standing on rock formation

The one one-kilometre-wide crater of Kawah Ijen, the largest highly acidic lake in the world (the pH of the water in the lake's edges is 0.5). The lake is the site of a labour-intensive mining operation, in which sulfur loads are carried by hand from the crater floor. Miners carry weights ranging from 75 to 90 kilograms (160-200 lb), up 300 metres to the crater rim, with a gradient of 45 to 60 degrees; then 3 kilometres down the mountain to the nearby Paltuding Valley for weighing and get paid. Most miners make this journey twice a night (to avoid the scorching heat), extracting some 14 tons everyday. They complain of numerous skeletal, respiratory and eye afflictions; their teeth slowly dissolve in the sulfurous vapours; they die of fatal accidents at a rate of 1,5 miners a year. Daily salary is around 8-10USD, making the job a mildly attractive option to its agricultural alternatives, paid at a net average of 120USD/month.