Almaden Quicksilver

Almaden Quicksilver park in San Jose used to be the site of the second largest mercury mine in the country. The state-of-the-art methods for extracting mercury from cinnabar polluted the area sufficiently that you can't eat the fish in Almaden Reservoir.

Interesting recent article on this area: http://www.tommangan.net/twoheeldrive/index.php/almaden-quicksilver-county-park-hiking-through-history/