In Burgundy, the town of Cluny still centers on an abbey that is only a fragment of what once stood there. In the 11th century, monks raised the Maior Ecclesia, the largest church built anywhere up to that point, and finished it in under seventy years, a construction feat that still puzzles historians given the tools and materials available at the time. The film rebuilds the lost basilica through detailed 3D reconstructions, layering them over the surviving ruins and the smaller church that occupies the site today, so the scale of what disappeared becomes visible rather than abstract. Historians and archaeologists walk the grounds and explain how Cluny grew from a single monastery into the center of a reform movement that reshaped religious life across medieval Europe, with hundreds of dependent priories eventually answering to it. The building's later demolition after the French Revolution gets its due as well, explaining why so little remains of a structure once considered one of the wonders of its age.