The first tower one encounters after Piazzale Labicano was rebuilt at the time of Pope Nicholas V (1445-1458); despite the absence of the coat of arms, the tower possesses the characteristics of the restorations attributed to this pontiff: the addition of a sloping wall in the lower part (scarp) and the gunports, whose tuff slabs with a central hole remain visible on the exterior. In the 20th century, ACEA installed a water tank inside the tower, which still exists and, from 1933, serves the nearby Eleniano Reservoir designed by architect Raffaele De Vico.
2. Tower of Nicholas V (1445-1458). Revision by C.Persiani in progress.