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 Monument, Kazanlak, Bulgaria; 2) Miles Glacier Bridge, Alaska, USA; 3) Bannerman's Castle, New York, USA; 4) Georg Thiele, Narvik, Norway
| Name | Type | Role | |
|---|---|---|---|
| Katherine 'Kate' Swanson | Producer | ||
| David Caldwell-Evans | Producer | Series Producer | |
| James S. Corum | Guest Star | Self - Military Historian | |
| Rob Bell | Guest Star | Self - Engineer and Adventurer | |
| Andrew Gough | Guest Star | Self - Historian and Author | |
| Viggo Kristensen | Guest Star | Self - Author | |
| Daniel 'Dan' Dickrell | Guest Star | Self - Mechanical Engineer | |
| Dougal Jerram | Guest Star | Self - Earth Scientist | |
| Roma Agrawal | Guest Star | Self - Structural Engineer | |
| Neil Caplan | Guest Star | Self - Bannerman Castle Trust | |
| Dora Ivanova | Guest Star | Self - Architect | |
| Lynette Nusbacher | Guest Star | Self - Military Historian | |
| Lucas Borer | Guest Star | Self - Childs Glacier Lodge | |
| Bruce Burgess | Executive Producer | ||
| Henry Scott | Executive Producer | ||
| Kyle McCabe | Executive Producer | for SCIENCE CHANNEL | |
| Katherine 'Kate' Swanson | Director |