It was the highest building constructed during the Middle Ages and is an architectural masterpiece. Built over hundreds of years, between 1176 – 1439, Strasbourg Cathedral is radically different from any other Cathedral. It built using new technologies and according to principles never tested before. For the first time, the researchers were able to trace in 3D the incredible history of this project. They reveal how the builders were able to defy the laws of physics to build higher and higher and explain the importance of iron in this stone cathedral. Director: Lionel Langdale Original Title: Extreme Constructions: The Secrets of Strasbourg Cathedral