Carved from 100 million pounds of stone, soaring effortlessly atop a spiderweb of masonry, Gothic cathedrals are marvels of human achievement and artistry. But how did medieval builders reach such spectacular heights? Consuming the labor of entire towns, sometimes taking 100 years to build, these architectural marvels were crafted from just hand tools and stone. Many now teeter on the brink of catastrophic collapse. To save them, an international team of engineers, architects, art historians and computer scientists searches the naves, bays, and bell towers for clues to how the dream of these heavenly temples on earth came true. NOVA's teams perform hands-on experiments to investigate and reveal the architectural secrets that the cathedral builders used to erect their soaring, glass-filled walls. This program reveals the hidden formulas, drawn from the pages of the Bible itself, that drove medieval builders ever upward.