The bridge has been there for almost 500 years, I think, with goldsmiths/jewellers occupying the shops on the bridge for much of that time. I think the corridor on the top was added to connect the Uffizi on one side with a palace on the other: it is now a gallery.
The story goes that late in WWII, the retreating German commander was ordered to blow up all five Arno bridges, but decided that he could not destroy Ponte Vecchio. A victory for civilisation?
Here you can see it via webcam.