The entrance to the cavity known locally as the “grotta di Milano” opens in proximity to the bed of the river Fibreno, along the north eastern slopes of the Colle Minghitto at 280 m a.s.l. The karstic cavity developed for 60 m (length ascertained so far) in the rudist- bearing calcareous rock of the Upper Cretaceous period. A low entrance, shaped like a wide dome, led into the first cave that was circa 20 m2 (A). From here a narrow passage led into a large gallery sloping steeply downwards whose walls were populated by numerous Orthoptera of the Trogolphilus species. At the end of the gallery were two caves with deposits of sub-fossil guano and moderate dripping. A short narrow cuniculus with a sub-circular section led from here to the exterior (at present it is blocked with earth). Also leading out from the two caves was a narrow passage which through a system of vertical fractures led to an upper level of the grotto, the deepest found so far, comprising a large cave with large stalagmites, circa 30-40 cm thick, which had broken off and fallen to the floor.

During the first excavation campaign a trench circa 6 m2 was opened, corresponding with the western half of the first cave (A) in the grotto. In 1986 Italo Biddittu found a flint scraper made from a levallois flake and fossilised faunal remains here which suggested that the cave was occupied during the middle Paleolithic period.
After the removal of the upper layers that contained no archaeological material – except for a few fragments of glazed pottery probably of medieval date – the upper part of a deposit was revealed which sloped steeply towards the interior of the grotto. This comprised breccia of middle to large dimensions overlying a layer of dark red earth, and covered in several points by crusts of concretions. Fossilised faunal remains were recovered from the surface of this level (including several deer teeth, a canine tooth of a hyena and numerous lateral fragments of apophyses from long bones, some showing signs of burning). Also found on the surface were rare limestone artefacts dating to the middle Paleolithic period.