A group of more than 150 steel furnaces stretching two kilometers across a hillside was recently discovered in Gansu Province.
The furnaces date from the Great Leap Forward, when the entire country was mobilized to turn scrap iron into steel using small-scale furnaces, with the aim of doubling the national output. The project was a total disaster and the furnaces were abandoned two years later.
And Frog in a Well:
Great Leap Forward era backyard iron furnaces have been unearthed [via] and there is discussion about whether to preserve them as historical evidence, even a cultural heritage.
Both articles provide interesting additional links.