Sanford Underground Research Facility (SURF)

A mile of Black Hills rock overhead is the point. Scientists at the Sanford Underground Research Facility need that rock to shield their experiments from cosmic radiation — searching for dark matter, studying neutrinos, asking questions about why matter exists at all. The facility runs inside the former Homestake Gold Mine in Lead, South Dakota, the deepest underground laboratory in the United States. The visitor center, free and open seven days a week, is the public's way in.