Lake Vermillion-Soudan Underground Mine State Park

The Lake Vermilion-Soudan Underground Mine State Park is a Minnesota state park at the site of the Soudan Underground Mine, on the south shore of Lake Vermilion, in the Vermilion Range. The mine is known as Minnesota's oldest, deepest, and richest iron mine. It formerly hosted the Soudan Underground Laboratory. As the Soudan Iron Mine, it has been designated a U.S. National Historic Landmark.

Source: Wikipedia