An investigation was made of the structures of the external fortifications of Castel Nuovo and successive transformations until the end of the19th century. The earliest elements found to date were situated west of the Castel Nuovo and comprised a circular tower linked to a curtain wall on an east-west alignment, faced with moulded blocks of piperno (lava stone). The structures can be associated with the so-called gate of the Aragonese citadel. The excavation also brought to light stretches of the western and northern walls of the bastioned town wall linked to the Torrione dell’Incoronata.

Inside the tower a vaulted room came to light; to the south it communicated with a cuniculus which was also vaulted. The latter was on a north-south alignment and its floor was constituted by a ramp paved in bricks interspersed with large rectangular blocks of lava stone placed edge up and with rounded ends. The ramp was suitable for carts and permitted communication inside the tower and passage from the second ditch.

The area delimited by the second ditch in the north-western sector of the bastioned town wall was already occupied in the Viceroy’s period by a series of buildings.

Lastly, in the south-eastern corner of piazza Municipio, in correspondence with the crossroads with via C. Colombo a trench was dug with the aim of checking the exact location of and the state of preservation of the Tower/Bastion del Molo of the fortification.
The surface of the opus caementicium core of the bastion appeared immediately below the present road. This probably dated to the 16th century phase.
Two imposing barrel vaulted communicating tunnels for rainwater collection dated to later restructuring of the area, undertaken during the 19th century. The construction of the tunnels made use of the cement nucleus of the bastion by cutting into its northern facing.