On August 19, 1418, a competition concerning Florence's magnificent new cathedral, Santa Maria del Fiore--already under construction for more than a century--was announced: "Whoever desires to make any model or design for the vaulting of the main Dome....shall do so before the end of the month of September." The proposed dome was regarded far and wide as all but impossible to build: not only would it be enormous, but its original and sacrosanct design shunned the flying buttresses that supported cathedrals all over Europe. The dome would literally need to be erected over thin air.

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