Archaeological excavations undertaken in Piazza Municipio during the construction of an underground station identified, in the 16th century ditch of the fortifications of Castel Nuovo, the portico and channels alongside an Angevin road linking the ancient town centre to the Reggia. Moreover, further remains of contemporary buildings were identified, probably relating to the palaces, known from the sources, which Robert of Anjou had built for his children and which must have stood alongside those belonging to the notables of the kingdom.

Investigations revealed the continuation of the structures, partially uncovered previously, belonging to the system of fortifications of Castel Nuovo, in particular the walls delimiting the third ditch outside the bastioned circuit wall. Three construction phases were identified, from the earliest which was the 16th century layout, when the wall delimiting the ditch presented an ample curve in correspondence with the circular tower of the bastioned wall, to the 18th and 19th century restructuring. In the late medieval period the part of the present piazza Municipio that was investigated was an open area, free of buildings, which must instead have occupied the adjacent zone, both to the north and west of Castel Nuovo. Inside the bulk of the ditch the only early medieval structure found was a well-cistern whose fill produced almost intact glazed and proto-majolica vases together with wooden finds. The late medieval structures rested on large natural progressive accumulations of an alluvial nature, formed between the 7th and 13th century. Below these accumulations, in the central part of the excavation, a road on an east-west alignment came to light. This was perhaps a branch of an extra-mural road that headed towards the port. It was constructed on compact sandy layers, delimited to the north and south by two roadbeds of building rubble. Ten levels of overlying beaten surfaces were identified, dating from the mid 6th century A.D. to the full 8th century A.D. The insertion of two parallel channels below the road, probably linked to the Serino aqueduct, dated to this latter phase. The road was flanked by burials, mainly concentrated in the southern area. Seven “a cappuccina” tombs were identified. In the absence of grave goods, the stratigraphy dated them to between the mid 6th and the 7th century A.D. Cultivated areas with holes for plants, supporting fences and channels for water drainage extended along the sides of the road, especially in the southern zone.

The excavation confirmed that the entire area had been occupied by the sea. In the basin investigated a succession of sea beds came to light belonging to the area closest to the bank where boats of low tonnage could enter and moor. Between 3 and 4.00 m below the present sea level, the latest sandy levels relating to 6th century A.D. occupation of the site were identified. In the northern part of the excavation the remains of wooden wharfs came to light of which the uprights embedded in the sand were preserved. The exploration produced numerous pottery and glass finds for this period. Below this level was evidence of a moment of stasis during the 3rd century A.D. when the structures of the preceding period were abandoned and obliterated. A quay at right angles to the coastline dated to the 1st century A.D. On an east-west alignment it was constituted by a dump of limestone rocks put together using the dry-stone technique and contained by vertical wooden posts. North of this structure three boats emerged: the first as it sank penetrated the flank of the second with its prow, thus damaging it. The boats seemed to have been abandoned close to the quay during the 1st century A.D. Their hulls were filled by the layers of sand that had formed in the 2nd century A.D. causing their complete obliteration. It was on this level that the two wharfs were constructed, their uprights penetrating the boats, by then covered with sand, breaking their planking. Two of the boats were commercial maritime vessels ( _onerariae_ ) used for small-medium sized coastal trading. The third was a rarer horeia, a large vessel with a flat bottom and prow with a vertical shaft. These were used in the port for loading and unloading cargo or for fishing. For the 1st and 2nd century A.D. phases many almost intact finds were discovered on the seabed. Furthermore, a great number of artefacts and instruments made of organic materials were preserved: boat equipment, fishing and work implements. At the beginning of the 5th century A.D. silting and swamping occasioned the abandonment of this part of the harbour basin and the advance of the coastline.

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.

Excavations continued around Castel Nuovo in piazza Municipio. The investigation continued with the exploration of the north-western part of the bastioned wall surrounding the second ditch and the buildings inside it, already partly uncovered. The wall delimiting the castle’s first ditch, the line of which is partly retraced by the present wall, was identified. This was a low crenellated structure dating to the restructuring of Castel Nuovo ordered by Alfonso d’Aragona. The facing was preserved on the north side almost to the top, whilst on the south side it was preserved from circa 4.75 m a.s.l. to a height of circa 3.10 m as it was cut into by modern reconstruction. This wall was respected even when the bastioned wall was built in the period of the Viceroy in the 16th century. The excavation revealed that, in this period, to the south it partly delimited a sloped surface which extended as far as the southern frontage of the rooms present in the second ditch and constituted one of the routes used for movement inside the ditches and communication between the latter and Castel Nuovo. This ramp, identified by a series of overlying beaten surfaces, with cart tracks impressed in their surfaces, datable to the 16th-19th century, was linked to the gate of the so-called Aragonese citadel. Below these floor levels the excavation revealed a stratigraphic sequence of rubble, obliterating earlier structures for which a date was indicated by the 15th century pottery found in the obliteration layers. Investigation also continued inside the building which stood in the second ditch. The rooms, belonging to these structures, functioned as arms stores, as attested by iron and limestone cannonballs found during the excavation. Although dating to between the end of the 16th and the 17th century, the continued research has begun to reveal earlier phases with different functions and a different layout of the area.