The famous dome of the Cathedral of Florence was a big deal for us. The first dome constructed since the Romans, it's also sort of a big deal for a lot of other people.
But, the dome isn't the only historically awesome thing about Florence's Cathedral.
We also saw the baptistery doors--the relief sculptures done by Ghiberti (he won in a competition with Brunelleschi, which is good because Brunelleschi then had his free time to construct the dome). Anyway, these beautiful bronze panels (1421) and the dome (1436) are pretty much the symbols of the birth of the Renaissance and we were pretty darn excited to be there seeing them in person.
Then, of course, there's the campanile (bell tower) by Giotto, who was one of the proto-Renaissance painters of Florence who got some things going in art like individualized faces, emotion, and perspective. (Here's a link to his most famous painting--Madonna Enthroned--which we saw in the Uffizi Gallery. It was huge.)
A final shot of the Cathedral with its three famous components--the octagonal baptistery at left, the dome in the middle, and the campanile to the right.