The Rio Tinto (Red River) in Spain has had a shitty time ever since humanity turned up. We’re not indulging in hyperbole, here; Homo sapiens have been dumping pollutants in the river for over 5,000 years, a number you may recognize as five times the combined duration of the Roman Empire and the Egyptian Empire. … The area was first mined by the Iberians and Tartessians in the third millennium B.C., and it remains a viable source of copper even today. Over time, it acquired its characteristic red color from heavy metals that crept in as a side effect of mining. The color’s not all that trickled in, either. The river is actually even more lethal than its uninviting appearance suggests. The pH of the water hovers around 2, placing it on par with stomach acid. Yes, Rio Tinto could literally digest you.