Roman bridge in Rome, which carried the Via Nomentana over the Aniene (Latin: Anio) River. Having laid outside the city limits for most of its history, the picturesque bridge is noted for its medieval bridge tower, which served to protect this important northern approach to Rome. The still intact fabric of the main arch dates from the late Republican era. The lower part of the bridge tower dates, according to an unproven tradition, from the time of Pope Adrian I (772-795), while the imposing castle-like structure was constructed during a general overhaul of the bridge by Pope Nicholas V (1447-1455).