Florence is a city of red roofs and marble-faced churches. Alot of activity revolves around the mighty Duomo, which has an incredible green, pink, and white marble façade. The doors are painstakingly carved. Near the Duomo, towards the river Alda, is the Piazza de Repubblica. This plaza was constructed to celebrate Florence's brief stint as Italy's capital (I think the dates when it was the capital are 1865-1871). Further towards the river is Palazzo Vecchio ("Old Palace" -- in the picture seen from the vantage of the statue of Duke Cosimo I) and the Uffizi Galleries (in the picture, seen from the upper floor of Palazzo Vecchio), which houses many famous paintings by Italian artists. From the top floor of Palazzo Vecchio you get some great views of the surrounding area.
Just next to the Uffizi is the great Ponte Vecchio ("Old Bridge"), which is the oldest bridge in Florence. It is actually far older than the other bridges because it's the only one the Germans didn't destroy in WWII -- they kept it out of respect (although they ripped down all the houses because it would not be a good vantage point if there was no line of sight anywhere on the bridge). From the Palazzia Michelangelo (something like that anyway) you can see back onto the central parts of town, including both of the "Vecchios" (by that I mean Palazzo Vecchio and Ponte Vecchio). Upon that same hill is a replica of Michelangelo's David, which is actually housed in a museum also in Florence.
A few other churches of note are: Sainto Spirito, San Lorenzo (which has a large market in front of it -- this picture includes a statue of the father of Duke Cosimo I), and Santa Croce, which has an open plaza in front of it.
[Sorry about the darkness in some of these outdoors pictures, the weather was less than perfect when I was in Florence.]
