A labyrinth of tunnels underneath a tiny French village which contains mysteries from several historical eras, and a Welsh slate mine that has been given a new lease of life.
Incredible feats of human endeavour, revealing what people have built, where, how and why.
A look at some of Switzerland's 300,000 subterranean bunkers built across history.
An underground city beneath a forest in Northern France built to house 3,000 people.
The underground bases built by the German army during the occupation of Jersey.
The secrets of the largest subterranean fortress along France's border with Germany.
The military headquarters built beneath Dover Castle during the Second World War.
Description: This series looks at just some of the buildings that were designed to fight Hitler.; Category: Military & War; 8 episodes available.
Description: Tim Dunn explores the stunning architecture that lines the railway network.; Category: Engineering; 40 episodes available.
Description: The history enthusiast honours Lancaster bomber crews of the Second World War.; Category: Military & War; 1 episode available.
Description: Guy builds a working replica of a WWI tank and drives it at a Remembrance Day parade.; Category: Factual Entertainment; 1 episode available.
Description: Guy Martin recreates technical achievements of the 19th century.; Category: Engineering; 6 episodes available.
Description: Guy joins the two-year restoration of a Spitfire that was buried in a French beach.; Category: Engineering; 1 episode available.
Description: Jamie Theakston investigates incredible tales from the annals of history.; Category: History; 11 episodes available.
Description: The rise of Nazi Germany's speed record cars of the 1930s.; Category: History; 1 episode available.
Description: An international team works on Australia's biggest ever tunnelling project in Sydney.; Category: Engineering; 8 episodes available.
Description: This ambitious, striking film challenges our understanding of the Second World War.; Category: History; 1 episode available.
Description: Examining the Industrial revolution - the age of smoke and steel.; Category: Engineering; 6 episodes available.
Description: Teams across the country are keeping our heritage standing, these are our landmark fixers.; Category: Engineering; 6 episodes available.