A strange complex of tunnels on the grounds of a bizarre mansion were under lock-and-key for a century, and since its rediscovery, some believe its mysterious place is a gate to hell. Stories: 1) Villa De Vecchi, Rhodes, Greece; 2) Nuttallburg, West Virginia, USA; 3) The Initiation Well, Quinta da Regaleira, Sintra, Portugal; 4) Botallack and Levant Mines, Cornwall, UK
| Name | Type | Role | |
|---|---|---|---|
| Tom Williams | Producer | ||
| Luke Wales | Producer | ||
| Mathilde Almesh | Guest Star | Self - Tour Guide, Quinta da Regaleira | |
| Jim Meigs | Guest Star | Self - Author and Journalist | |
| Fran Scott | Guest Star | Self - Scientist | |
| Chorafitus Eleftherios | Guest Star | Self - Tour Guide, Villa De Vecchi | |
| Dougal Jerram | Guest Star | Self - Earth Scientist | |
| Charlotte Tomlinson | Guest Star | Self - National Trust Site Manager, Levant Mine | |
| Andrew Gough | Guest Star | Self - Historian and Author | |
| Shini Somara | Guest Star | Self - Engineer | |
| James S. Corum | Guest Star | Self - Military Historian | |
| David Fuerst | Guest Star | Self - National Park Ranger | |
| Dominic Selwood | Guest Star | Self - Historian and Author | |
| Neil Laird | Executive Producer | for SCIENCE CHANNEL | |
| Bruce Burgess | Executive Producer | ||
| Henry Scott | Executive Producer | ||
| Tom Williams | Director | ||
| Luke Wales | Director |