Finnish for “hiding place” is onkalo; it is also the name for the first-ever permanent burial ground for spent nuclear waste, now being built in Finland to house that country’s radioactive waste. The film takes us inside Onkalo, a deep and vast man-made cave excavated more than four kilometers into the earth. When it is finished in the twenty-second century, it will be covered and sealed for eternity. Filmmaker Michael Madsen has made a poetic and haunting film about this eerie place, and in it he asks many probing questions, including most agonizing of all: How do we protect the people of the far future from Onkalo and what it holds?—a question made all the more on point after the recent disaster at the Fukushima plant in Japan.