The magnificent dome atop the cathedral in Florence, Italy is not only one of the wonders of the Renaissance, it is considered a miracle of modern engineering. The cathedral was designed to be the largest in the world but there was a problem: it was so huge, no one knew how to build a dome large enough to finish it off. For fifty years the altar remained open to the elements, until Filippo Brunelleschi convinced the town fathers he could do the impossible. How Brunelleschi succeeded is one of the great technical, artistic, and human sagas of all time.