A Mediterranean island paradise is not all that it seems; its complex of abandoned buildings were once prisons for the world's most dangerous Mafiosi; experts investigate new evidence to reveal who was imprisoned here and the secrets they left behind. Stories: 1) Fort Saint Elmo, Valletta, Malta; 2) Dredge Number 5, Nome, Alaska; 3) Alddreu Airfield, Jeju Island, South Korea; 4) Asinara Island, Sardinia, Italy
