Pretty much everything in Florence is a famous piece of art and/or some kind of symbolic structure. But whenever I think back to the Tuscan city, the image that always comes to mind is the Duomo.
I mean, guys, the thing is massive! And very photogenic. Of course, I always knew it as the home of Brunelleschi's dome, which was one of my favorite stories when learning about the Renaissance. Basically, to decide on who should be the architect of the of the dome, the powers that be said the man to get an egg to stand on it's end could do it. So Brunelleschi, being a 15th century Italian smart ass, flattened the end of his egg so that it stood up easily, thus securing himself the job. My kind of guy!
One of my favorite parts of the Duomo was climbing up to the top of the dome. At one viewing level, you actually walk around the inside base of the dome, up close and personal to ornate painting that covers it. The view from the top wasn't that bad either!
Even though we only spent one afternoon actually exploring the Duomo, it was pretty much a constant of our trip to Florence. We walked by it more times than I can count and snapped pictures of it from every other museum/church/building we visited! A definite Florence must-see/can't-miss!