They were nicknamed mangiacode ('tail-eaters'), after the typical dish coda alla vaccinara, which was a specialty of the many vaccinari ('butchers') of the rione.

In the Middle Ages it entered the fourth of the seven new ecclesiastic regions, even if at that time the limits of the rioni were not very clear.

In 1875, after the walls to stop the floods of the Tiber were built, the look of the area changed completely, removing all the things that grew up close to the river during the centuries.

Though small, the rione contains many kinds of buildings: palaces, hospitals, churches, embassies, ancient prisons and poor houses.

To the east, it borders with Sant'Angelo (R. XI), from which is separated by Via di Santa Maria del Pianto and Piazza delle Cinque Scole, up to the Tiber.