El Teniente

El Teniente ("The Lieutenant") is an underground copper mine in the Chilean commune of Machalí in Cachapoal Province, Libertador General Bernardo O'Higgins Region, near the town of Sewell, 2,300 m (7,500 ft) above mean sea level in the Andes.

Mining at El Teniente is reported to have started as early as 1819. Kennecott Copper Corporation ran the mine through a subsidiary company up until the Chilean nationalization of copper and the formation of the state owned copper mining company Codelco who currently operates the mine. It is reported as "the world's biggest underground copper mine", and is the largest of Codelco's operations.