At Aia del Castellare, the fourth excavation campaign took place between the 27th June and 16th July 2011. The team comprised members of various Italian universities and associations.

Eleven quadrants were investigated, situated in the areas to the east and west of the aqueduct. In particular, the research concentrated on the part of the deposit to the east of the line of the aqueduct del Fiora (quadrants H-I-J 2, 1, 0, -1), but small trenches were also dug in the western part of the site (quadrants C-D 3, D 2).

In the eastern sector, it was seen that the white, heavily concretionary layer containing abundant lithic industry and faunal remains, previously identified at about 40-50 cm below present ground level, extended into the new quadrants (H-I-J). In the same quadrants, the stratigraphy previously observed at 140-190 cm below present ground level (due to the hill slope), laying between a fine white, heavily concretionary sediment and an underlying yellow, sandy, very compact layer, seemed to become darker and more compact as it went down. At the edge of the hill slope, several stalagmitic formations attested the earlier existence of an underground chamber, as seen in the western sector last year.

The deposit in the western sector examined during this campaign (quadrants C-D) appeared to present the same stratigraphy as that seen in the eastern quadrants. The trench’s limited extension prevented further observation.

In both sectors, abundant quantities of lithic material continued to be found, well-preserved and without any surface alteration. The material was characterised by an ample use of the bifacial technique and the mainly medium to small dimensions, which from a typological point of view can be attributed to a very early and modestly attested period of the Italian middle Palaeolithic period. A considerable quantity of faunal remains also came to light, including bear.