The investigation aimed to gain an understanding of the medieval phases of the monument’s use. A number of rooms in the Ist order (ground floor) were examined, as were a space below the stairs of cuneo III on the third level and all of cuneo X (space below the stairs, in front of the radial corridor and part of the third level). The present floor level, created by 17th century restructuring, from which the excavation began, coincides approximately with the ancient one. The excavation investigated the layers which had formed, following the almost total robbing of the ancient flooring, between the _opus caementicium_ of the Flavian foundations and the level fixed after the in-fills of the 19th century, which eliminated all modern and part of the late medieval stratification. In cuneo III the layer filling the robbing of the ancient paving, although cut and disturbed by later interventions, fixed the chronology of the robbing to the second half of the 12th century, in agreement with what has been documented in the innermost part of cuneo X, the ambulatory and radial corridor. The situation was more complex in the area below the stairs in cuneo X. Here, the excavation exposed various occupation phases following the removal of the paving. During the 12th century, soon after the robbing of the paving slabs and almost at the level of the Flavian foundations, the opening onto the ambulatory was closed by a wall (of which only a slight trace remains) and an uneven beaten earth floor was put down. On the rear side, abutting the ancient wall which closed it, a structure was built with stones of varying sizes and lime mortar, perhaps a counter, of which only the lowest part is preserved. A hearth constituted by a circle of stones, suggests that this space may have been used as a dwelling. This evidence shows that types of temporary dwelling, for which both archaeological and documentary evidence is very scarce, still existed in the late medieval period. Subsequently, during the first half of the 13th century, the space was radically modified. The floor level was raised by up to 30 cm by a dump of earth and stones, and a new uneven floor surface was created. The structure up against the back wall, and the wall which had closed it off from the ambulatory were demolished. A new structure was built up against the east wall, constituted by a wall about 1.20 m high and about 5 m long, abutted by a tank made up of a thick layer of opus signinum. It is likely that this transformation marked a change in use for this space, it may have become a storeroom, animal stall or been used for production activities that have yet to be defined. In the 13th century it fell out of use, as attested by the robber trenches of the Flavian stone block walls which had delimited the space. It was covered by silt deposits, cut by 17th century digging. The upper part of the stratification was constituted by the layers relating to the reconstruction undertaken in the first half of the 19th century.

In June 2014, Rome University, in collaboration with the Special Superintendency for the Colosseum, the MNR and Archaeological Area of Rome, resumed activities inside the Flavian amphitheatre, as part of a project aiming to document the post-antique use of the monument. In 2011-2012, the excavation of _cunei_ III and X was completed. Therefore, in 2014, a new area was opened in _cuneo_ IX. Here too, the removal of the paving slabs during the 12th century caused the loss of the stratigraphy that had built up in late antiquity and the early medieval period. However, these phases were preserved inside the sewer pipes, which had kept a complex stratigraphy intact, dating from the 2nd century A.D. onwards. The evidence showed that during the later medieval period each _cuneo_ underwent independent and differing changes, including many different types of use. In this _cuneo_, the first occupation evidence found, post-dating the removal of the ancient paving, related to the division of the space into two parts with the construction of a transverse wall. Later, this was almost completely removed and substituted by another structure built using reused materials and moved back about 50 cm towards the arena. The restructuring eliminated the area’s earlier function as a passageway, probably transforming the space into one of the numerous _cryptae_ that are mentioned in written sources and which characterised the monument between the 11th and 13th centuries. The traces of housings in the ancient walls of travertine and tufa blocks attest the use of the outermost part as a stable or storeroom. In the same phase as the one that saw the construction of the dividing wall, a wattle and daub structure was built in the outer room, running parallel to the west wall of the amphitheatre. However, its function, certainly linked to the creation of the _crypta_, remains to be clarified. During the 14th century, the ancient structure of this _cuneo_, like the adjacent one, was systematically robbed of the travertine blocks. With the consequent collapse of the sidewalls, and probably most of the roofing, the _crypta_ fell into disuse, the transverse wall was demolished and the space was once again used as an entrance leading into the arena from the outside. This function remained throughout the modern era, until the substantial transformations linked to the excavations and restoration of the Napoleonic period.