The Time Team travels to Blaenavon, Wales, to solve a massive historical mystery: what happened to the world’s first railway viaduct? Built at the dawn of the Industrial Revolution, this 10-arch giant disappeared from records by 1815. Using heavy artillery machinery and advanced radar, the team attempts the deepest excavation in the show’s history to find a structure buried under 10,000 tons of debris. Discover the harsh reality of 18th-century ironworks and see the moment a remote camera captures the first glimpse of the viaduct in two centuries.