To kick off the list, we're going to go back. Way back. Filippo Brunelleschi, born in Florence, Italy, in 1377, was one of the early masters of modern architecture. His innovative work would have an enormous impact on many of the great Renaissance men to follow, as Brunelleschi's real brilliance lay in his engineering. When the Florence Cathedral was in need of a new dome, Brunelleschi was confident he could accomplish something that had never been done in modern times: Erect a completely self-supporting dome.
He was hampered by two seemingly minor (to us, anyway) complications. First, the recipe for mixing concrete had gotten misplaced during the whole Falling of Rome fiasco. And second, there was the decided lack of giant forests in the area, from which vast amounts of scaffolding could be made. So not only was Brunelleschi trying the unthinkable, he didn't even have the two main raw materials that would have made the entire thing seem remotely doable.
Nonetheless, a mere 4 million bricks and 16 years later, the Florence Cathedral had a dome, one so awesome for the era that the pope himself came to consecrate it on Easter Sunday in 1436 and it's still a architectural landmark to this day [source: PBS].