The Rio Tinto, a 100 km long river in Southern Spain that originates in the Sierra Morena mountains of Andalusia.

The water of the river which flows from the city of Pena de Hierro to the Atlantic Ocean in Huela is red in color because of high concentration of ferric iron.

The river has serious environmental problems due to heavy concentration of metals and low pH.

In the last 5000 years, the site along the river has been mined for copper, silver, gold, and other minerals.

Iberians and Tartessians a group of people in 3000 BCE began mining the site which was later followed by the Phoenicians, Greeks, Romans, Visigoths, and Moors.

The mines were rediscovered in 1556 after a period of abandonment. In 1724 the Spanish government began operating those mines. The Río Tinto is very famous for being very acidic (pH 2) and its deep reddish hue is due to iron dissolved in the water.