A strange alien shrine on a mountain peak, a bridge built in the Alaskan wilderness, and an American castle with a dangerous secret are mysterious deserted engineering projects, and new discoveries reveal how they were built. Stories: 1) Buzludzha... (more) Monument, Kazanlak, Bulgaria; 2) Miles Glacier Bridge, Alaska, USA; 3) Bannerman's Castle, New York, USA; 4) Georg Thiele, Narvik, Norway

Andrew Gough, Daniel 'Dan' Dickrell, Dora Ivanova, Dougal Jerram, James S. Corum, Lucas Borer, Lynette Nusbacher, Neil Caplan, Rob Bell, Roma Agrawal, Viggo Kristensen