Sewell is a Chilean mining town which has been declared a UNESCO World Heritage Site. It was developed by the Braden Copper Company in the past to house the workers and their families associated with the El Teniente mine, the world's largest underground copper mine. At its peak in 1960, the town had a population of 16,000 people. After the nationalisation of copper mining in 1971, the Chilean government moved the workers to the valley and built the Copper Highway for commuting access to the mine and other operations. Some of the buildings were destroyed in the 1980s, but some have now been restored due to the town being declared a National Monument in 1998.