earlier post mentioned Brunelleschi’s Dome that sits atop the Florence Cathedral (Il Duomo di Firenze), and here is a view looking up into the dome. There are many things about this dome that are remarkable. The dome caps an octogonal hole that is 150 wide that was open to the elements for over a hundred years. The original builders of the cathedral did not know how to complete the crown that would start atop 180 foot walls. This was 600 years ago, long before architecture or engineering was a science and construction was more of a trial and error affair.
After much discussion and a competition Brunelleschi was chosen for the task, a man with no formal architecture training. He was by trade a goldsmith.
National Geographic has a series of articles and graphics that provide a lot more detail of this fascinating accomplishment.
Shown in the above photo is the fresco that was later added inside the dome. The credit for that work goes to three men, Vincenzo Borghini, Giorgio Vasari and Federico Zuccaro.