Deep in an abandoned German salt mine, barrels of nuclear waste lie in a jumbled heap—untouched since the 1970s, when this picture was taken.Since the 1960s the Asse II chambers in Lower Saxony (map) has been a storage site for more than a hundred thousand barrels of low- to medium-level nuclear waste. Low-level waste isn't considered dangerous to handle, but medium-level waste may need shielding before disposal—such as encasing reactor components in concrete—according to the World Nuclear Association, which promotes nuclear energy.