Last week I told someone here that I had not taken any
photos of this bridge on my recent trip to Rome, but then saw
that I had. It's the Ponte Rotto, or "broken bridge," aka
Pons Aemilius, the oldest stone bridge in Rome—
built in the 2nd century BC! Only one arch is left, and the
new bridge directly behind it is the Ponte Palatino.
[You can see more Sunday Bridges here, chez Louis la Vache.]