In the city of Beauvais, located in the Oise department of northern France, the Saint-Pierre Cathedral holds a unique place in architectural history. Built starting in 1225, the cathedral was designed with extraordinary ambition, featuring the highest Gothic vault ever constructed in medieval Europe—48 meters high. This feat of engineering was meant to showcase the architectural boldness and cultural prestige of the era. The cathedral’s bishop aimed to create the largest Gothic structure in France, surpassing even the famed cathedrals of Amiens and Paris. On November 28, 1284, the vault of the cathedral’s choir collapsed. Historians agree on the event itself, but the exact cause remains debated. One widely accepted explanation points to design flaws, such as weak piers and insufficient buttresses that compromised the structure’s stability. Another theory, supported by the cathedral’s official website, suggests that strong winds, possibly during a storm, played a role. More recent studies propose a resonance phenomenon, where wind vibrations caused the building to resonate and collapse. Reconstruction began in 1338 under the architect Enguerrand le Riche, and was completed by 1347. To prevent future collapses, intermediate pillars were added and metal tie rods were installed between the buttresses. However, the cathedral’s architects again took a gamble with height. Instead of extending the nave to stabilize the structure, as was the architectural norm, they built a lantern tower with a spire at the crossing of the transept. Completed in 1569, this addition was visually striking but structurally risky. The spire and part of the bell tower collapsed in 1573, just months after its completion. A report by the King’s masons had previously warned of structural weaknesses, including the settlement and bending of key pillars. The collapse of the spire and bell tower severely hindered the cathedral’s development. The costs of rebuilding the vaults were so high that the nave, which could have provided much-needed stability, was never completed. In a final attempt to stabilize the structure, a small nave was hastily built, but the work was abandoned, leaving only a single bay of the nave completed. Today, the Saint-Pierre Cathedral remains under close monitoring. Since the 1960s, the removal of metal tie rods—once crucial for stability—led to renewed cracking in the transept. These rods were reintroduced in 2003-2004. In recent years, a major restoration project has been underway, led by the DRAC Hauts-de-France. The project involves removing temporary wooden bracing installed in 1993 and replacing it with more permanent reinforcements. A network of sensors tracks the slightest movement of the masonry, ensuring the building remains stable during the work. The project, initially set to finish in 2026, aims to preserve the cathedral's legacy and finally complete the unfinished dream of its medieval builders.