A breathtaking stainless steel tower seems otherworldly and out of place in the remote mountain forests of Croatia; experts investigate and uncover a dark past of Nazi-led conflict and a monument to a desperate fight for survival. Stories: 1) Brooklyn Army Terminal, New York City, New York; 2) Armero, Colombia; 3) Crossness Pumping Station, London, England; 4) Petrova Gora, Croatia