Two former saltpeter refineries located in northern Chile, in the Atacama Desert. Founded in 1872, the Saltpeter works and the towns constructed around them became obsolete fifty years later, after two German scientists Fritz Haber and Carl Bosch, synthesized ammonia, which meant fertilizers could be produced more efficiently and more cheaply.
In 1970, after becoming ghost towns, Humberstone and Santa Laura were declared national monuments and opened to tourism. One year later, president Salvador Allende declared also Chacabuco a Historic Monument of Chile, but in 1973, after the military coup, Pinochet turned it into a concentration camp until the end of 1974.
Still a dangerous place today, Chacabuco is surrounded by landmines left by the Chilean army. In 2005 Humberstone and Santa Laura were declared a World Heritage Site by UNESCO, whereas Chacabuco remains a hidden evidence of industrial decay and regime brutality.