Deep underground mines, for example South African gold mines and the Pyhäsalmi copper and zinc mine in Finland, have provided opportunities to sample the deep biosphere. The deep subsurface has also been sampled at chosen or proposed nuclear waste repository sites (e.g. Yucca Mountain and the Waste Isolation Pilot Plant in the United States, Äspö and surrounding areas in Sweden, Onkalo and surrounding areas in Finland, Mont Terri in Switzerland). Scientific drilling of continental deep subsurface has been promoted by the International Continental Scientific Drilling Program (ICDP).