Worker carrying a sack of salt on his shoulder in Salineras (salt evaporation ponds) in Maras, Peru. Salt has been harvested in Maras since the time of the Inca Empire. The site has around 3000 ponds of 5 square metres (54 sq ft) each. As the location is surrounded by salty mountains, subterranean water deposits the salty water in the ponds; the water evaporates due to the exposure to the sun. After approx. 1 month the level of salt reaches 10 centimetres (3.9 in) and is removed in sacks.