A single arch is all that remains of the Pons Aemilius, better known as the Ponte Rotto (Broken Bridge), the first bridge in Rome to be built completely out of stone.
The piers of Pons Aemilius were built in 179 BCE and were connected by stone arches in 142 BCE. Over the course of time it was rebuilt on several occasions. In 1598 a catastrophic flood destroyed half of the bridge. This time it was not rebuilt, but abandoned for the next two hundred and fifty years.
In 1853, Pope Pius IX (r. 1846-78) had the remains of the Ponte Rotto connected to the left bank of the river by an iron bridge. In 1887, the iron bridge, and all but one arch of the Ponte Rotto, were destroyed in order to make way for the Ponte Palatino (also known as the Ponte Inglese), the work of the engineer Angelo Vescovali (1826-95).
A photograph (1876) of the Ponte Rotto and the iron bridge extension