In 2016, the trench opened in 2015 was extended to the north and this completed the excavations of an entire section of the amphitheatre, from the external floor level to the arena, documenting its architectural typology and construction techniques. In 2015, only the foundations and robber trenches were uncovered, this season the excavations showed that in some sectors of the building the structures were very well-preserved, standing up to 1.70 m high.
To date the structures brought to light at a maximum depth of 3.17 m below ground level (0.28 m a.s.l.) are, from the exterior to the interior:

- A 6.90 m wide sector of a_ platea_ that continued beyond the trench edge. This was probably the paving outside the amphitheatre and not the foundation of an external gallery as suggested in 2015: therefore, the amphitheatre did not have an external gallery and its dimensions can be reconstructed as about 142 × 107 m; – a complete radial wall from the external radian and parts of a further three, built in opus caementicium faced with small limestone blocks and attested to the north of an elliptical wall. The complete radial wall was 10.20 m long and 0.80 m wide and was situated south of a robbed-out pillar. The upper surfaces of the walls presented clear traces of the sesquipedales that were originally set in mortar and later removed, evidence that constructions in opus listatum had tile courses. The distance between the walls was not regular: in two of the spaces between them there were two opus caementicium structures, which probably served to support the stairs leading up the cavaea; – the elliptical wall to which the external ends of the radial walls joined to the south, uncovered for a length of 10.70 m and to a height of 1.70 m, characterised by a very well-finished facing of small limestone blocks with regular mortar stilatura grouting; – the two walls belonging to the inner radian of radials, heavily cut to the south and north (where there was evidence of two pillars) by robbing. Between these walls, there was also an opus caementicium structure that supported a staircase. These structures show that the amphitheatre of Aquilea was a “hollow structure”, disproving the hypothesis sustained in the past that the arena had been excavated into the terrain; – a section of the elliptical podium foundation, 2.15 m wide and built in opus caementicium; – a section of a 0.50 m wide elliptical wall built in stone blocks, which delimited the arena space and perhaps constituted the northern parapet of a drainage channel that must have run at the foot of the podium to collect rainwater running off from the seating tiers, – a limited area of the arena whose floor seemed to be constituted by a sandy-clay layer, below which a layer of building materials emerged, mainly constituted by painted plaster fragments and two sesquipedales aligned east-west, whose significance will be clarified during future investigations. In fact, the excavation of this layer could provide useful material for dating the structure, particularly as dating was compromised in other sectors by the impossibility of reading the construction site phases due to a rise in the water table.

From a technical point of view, this year’s excavations also confirmed that the wall foundations were constituted by a substantial make up traced on the terrain prior to the construction, which laid out the lines of the radial and elliptical walls. From a diachronic point of view, it was seen that some sectors of the amphitheatre were reused in the late antique-medieval period for dwellings, which exploited the standing ancient walls. The open space of the arena was reused for agricultural purposes.