The hypogeum of St. Saba in Rome, found in the area of the medieval basilica in March 1900, is a relevant example of late-Roman buildings transformation into religious spaces (late 6th - early 7th centuries). At the same time, it represents an explicative case to illustrate the links between different investigative approaches, coming from archaeological, historical-artistic and historical-architectural point of view. In fact, since the excavation undertaken by the Associazione Artistica fra i Cultori di Architettura, the historiographical debate on the apsidal hall has been nourished by numerous scholars who have attempted to interpret the surviving remains in order to reconstruct the primitive events of the place of worship.Historical architecture cognitive process is articulated through different methods of investigation, each time calibrated according to both the characteristics of the pre-existence and the problems of knowledge. In the case of St. Saba, the results of the excavations of the early twentieth century have been compromised by the interventions carried out during the works, the fragmentary nature of the surviving remains and the limited extension of the investigation. The following studies – relating to historical sources, typological characteristics, constructive aspects and the decorative apparatus of the factory – partly integrated the incomplete data, re-elaborating, from an interpretative point of view, the theses formulated at the beginning of the last century.However, some unanswered questions remain, partly related to the architectural events of the building; integrating the results of different disciplinary contributions, the surveys conducted on visual surfaces make it possible to restore the peculiarities of the primitive space and its transformations. ; L’aula ipogea di San Saba a Roma, rinvenuta nell’area di sedime della basilica medievale nel marzo del 1900, costituisce un significativo esempio di trasformazione di un ambiente romano tardoantico in spazio religioso (fine ...