The Berkeley Pit is an abandoned open pit copper mine located in Butte, Montana, United States. It is over a mile long, half a mile wide, and over a third of a mile deep. During its heydays, Berkeley Pit supplied a sixth of the world's copper needs, and during the 27 years of operation approximately 320 million tons of the ore were extracted enough to “pave a four-lane highway four inches thick from Butte to Salt Lake City and 30 miles beyond,” according to Pitwatch.org. The once thriving copper mines of Butte earned the district the title of “the richest hill in the world.”

Today, the pit is filled with nearly 30 billion gallons of highly acidic water laced with toxic chemicals like arsenic, cadmium, zinc, and sulfuric acid that threaten the environment and the water supply of the nearby town of Butte.

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