Beneath the streets of Paris lies a parallel universe – a maze of tunnels and ancient quarries stretching for over 180 miles. These quarries provide the building blocks for the city, but now they threaten it with collapse. The film strips away Paris’s most famous icons to reveal their secret inner workings and the ingenious technology that allowed engineers to build the Eiffel Tower, Notre Dame and Sacre Couer. We peel back the boulevards to reveal the threat that lies just 60 feet below ground. We descend into the city’s caverns to meet the engineers and geologists working to prop up the streets above and join the team constructing a brand new metro line in the city’s already crowded underground world. CGI animation strips away the Eiffel Tower’s and exposes its foundations that drop just 17 feet below the surface. We join the team building Paris’s newest skyscraper to see how this same ‘light touch’ design is helping them transform the city’s skyline.