The beautiful Salineras salt mines in Maras, Peru. The salt comes from a subterranean stream. The water comes out at a spring by the mines. The flow is channeled into many tiny canals that direct the water gradually downslope to the numerous terraced pools. They are shaped into polygons with the flow of water carefully controlled and monitored by the workers. The altitude of the pools slowly decreases, so that the water may flow through the myriad branches of the water-supply channels and be introduced slowly through a notch in one sidewall of each pond.