An enormous concrete box with bizarre circular openings looms on the coast of an island near mainland China; Experts investigate and uncover tunnels leading to an enormous underground complex that nearly triggered a nuclear war. Stories: 1) Kinmen Island, Taiwan; 2) Kennecott Mining Town, Alaska; 3) Jarlshof Settlements, Shetland, Scotland; 4) Fortress Furggels, Pfafers, Switzerland