During 2008-2009 substantial restoration work was undertaken at Rocca Cerbaia, which concluded the first phase of a programme for the creation of an archaeological park. The restoration work was flanked by an archaeological watching brief. The area corresponding to the line of the first curtain wall was the object of substantial excavations. The work, aimed towards a partial reconstruction of the curtain wall which was necessary in order to provide better and safer access to the site, looked to identify the traces of the defensive structure that were still present, in order to define their plan and the dynamics of the collapse.

The excavation investigated a steeply sloping area situated to the south of the pentagonal palace. It was seen that the walls, of which short stretches of the rubble core remained, following the profile of the rock, had been built at the foot of the highest part of the summit, directly on the rock which had been levelled without the cutting of a foundation trench. Therefore, the curtain wall fanned out in a series of obtuse angles, which came to form six sides and followed the profile of the rocky outcrop quite closely. The deep archaeological deposit was constituted by elements of collapse which appeared as single ashlar blocks associated with lumps of mortar, and as substantial sections of wall conserving at least one or in some cases both of the facings. Two of these sections, cleaned and left in situ, to attest the original line of the wall and the collapse of the structure itself, correspond to two different corners of the defensive structure. On one of the sections traces of aligned putlog holes were present. Another smaller section of wall was interpreted, on the basis of construction technique and its width, as part of the collapse of the palace above. Due to the absence of dating elements it was not possible to define the chronology of the collapse with precision. However, it appeared to be the result of a long diachronic process during the period of post-medieval abandonment of the site. The causes seem to be found in the formation of the rocky substrata, which due to its scarce cohesion leads to slippage towards the south (even today) of the different rock layers, as attested by the position of the collapsed walls themselves, which appear to have slipped and not tumbled.