Gothic cathedrals like Beauvais and Chartres rose hundreds of feet into the sky centuries before engineers had calculus, steel, or any way to model stress on paper. This NOVA film follows historians and engineers trying to reconstruct how medieval masons pulled that off, using flying buttresses, ribbed vaults, and pointed arches to shave enormous weight off stone walls while still holding up a roof. Beauvais Cathedral gets special attention as the cautionary case, a structure pushed so close to its limits that parts of it collapsed, twice, and the film uses that failure to explain exactly what the buttresses were fighting against. Modern engineers build scale models and run stress tests to check theories the original builders could only have arrived at through trial, error, and inherited craft knowledge passed down through generations of stonemasons. The film treats the cathedrals as engineering problems first, tracing how each innovation, from the pointed arch to the flying buttress, solved a specific structural failure that came before it, rather than as static objects of religious awe.