A vast open-pit copper mine on the eastern edge of Uptown Butte, abandoned in 1982 and slowly filling with rainwater so acidic and metal-laden that it dissolves bird droppings. The lake — over 1,700 metres long and now more than 350 metres deep — is one of the largest bodies of contaminated water in the country, and an active Superfund site.
A viewing platform at the rim lets you look down into it for a small fee. There is a short narrated history and the engineering of the ongoing water treatment is explained. The pit is bizarre, awful, fascinating — and the most direct way to understand what mining did to and for the city.